%0 Journal Article %J Bioengineered %D 2024 %T Exopolysaccharide from marine microalgae belonging to the \textit{Glossomastix genus: fragile gel behavior and suspension stability %A Dulong, Virginie %A Rihouey, Christophe %A Gaignard, Clément %A Bridiau, Nicolas %A Gourvil, Priscilla %A Laroche, Céline %A Pierre, Guillaume %A Varacavoudin, Tony %A Probert, Ian %A Maugard, Thierry %A Michaud, Philippe %A Picton, Luc %A Le Cerf, Didier %K fragile gel %K Glossomastix %K Microalgae %K Polysaccharide %K RCC3688 %K RCC3707 %K stabilizer %X With the aim to find new polysaccharides of rheological interest with innovated properties, rhamnofucans produced as exopolysaccharides (EPS) in a photobioreactor (PBR) and an airlift bioreactor (ABR) by the marine microalgae Glossomastix sp. RCC3707 and RCC3688 were fully studied. Chemical characterizations have been conducted (UHPLC – MS HR). Analyses by size-exclusion chromatography (SEC) coupled online with a multiangle light scattering detector (MALS) and a differential refractive index detector showed the presence of large structures with molar masses higher than 106 g.mol−1. The rheological studies of these EPS solutions, conducted at different concentrations and salinities, have evidenced interesting and rare behavior characteristic of weak and fragile hydrogels i.e. gel behavior with very low elastic moduli (between 10−2 and 10 Pa) and yield stresses (between 10−2 and 2 Pa) according to the EPS source, concentration, and salinity. These results were confirmed by diffusing wave spectroscopy. Finally, as one of potential application, solutions of EPS from Glossomastix sp. have evidenced very good properties as anti-settling stabilizers, using microcrystalline cellulose particles as model, studied by multiple light scattering (MLS) with utilization in cosmetic or food industry. Compared to alginate solution with same viscosity for which sedimentation is observed over few hours, microalgae EPS leads to a stable suspension over few days. %B Bioengineered %V 15 %P 2296257 %8 dec %G eng %U https://doi.org/10.1080/21655979.2023.2296257 %R 10.1080/21655979.2023.2296257 %0 Generic %D 2023 %T Biological and genomic resources for the cosmopolitan phytoplankton Bathycoccus: Insights into genetic diversity and major structural variations %A Dennu, Louis %A Devic, Martine %A Rigonato, Janaina %A Falciatore, Angela %A Lozano, Jean-Claude %A Vergé, Valérie %A Mariac, Cédric %A Jaillon, Olivier %A Team, The Dark Edge genomics sampling %A Sabot, François %A Bouget, François-Yves %K RCC1615 %K RCC1868 %K RCC4222 %K RCC4752 %K RCC5417 %K RCC685 %K RCC716 %X Population-scale sequencing has become a standard practice to explore the natural genetic diversity underlying adaptation, notably in land plants. However, current sequencing initiatives for eukaryotic phytoplankton primarily concentrate on creating reference genomes for model organisms and characterizing natural communities through metagenomics approaches. Consequently, few species have been thoroughly sequenced and intraspecific genetic diversity remains virtually undescribed, limiting our understanding of diversity and adaptation mechanisms. Here we report a biological and genomic resource to explore the genetic diversity of the cosmopolitan and ecologically important Bathycoccus genus. To span broad geographical and temporal scales, we selected available strains but also isolated and genotyped strains from both the Banyuls bay (Mediterranean sea) and the Baffin bay (Arctic ocean). By combining ONT long reads and Illumina short reads technologies, we produced and annotated 28 Bathycoccus sp. de novo assembled genomes of high quality, including 24 genomes of Bathycoccus prasinos strains along a latitudinal gradient between 40° and 78° North, one reference genome of the Bathycoccus calidus species and 3 genomes of a yet undescribed Bathycoccus species named Bathycoccus catiminus. We assessed the genetic diversity of this genus through phylogenomic analyses and highlighted the central role of this genomic resource in providing new insights into the diversity of outlier chromosomal structures. The Bathycoccus biological and genomic resources offer a robust framework for investigating the diversity and adaptation mechanisms of eukaryotic phytoplankton in the Ocean. Significance statement Comparative and functional approaches for the study of eukaryotic phytoplankton and their adaptation to latitudes and seasons that rely on extensive biological and genomic resources are currently lacking. Here we report such resources and describe the natural diversity of the cosmopolitan phytoplankton Bathycoccus, providing insights into its species and intraspecific diversity and establishing it as a robust model for functional and ecological studies. %I bioRxiv %8 oct %G eng %U https://www.biorxiv.org/content/10.1101/2023.10.16.562038v1 %R 10.1101/2023.10.16.562038 %0 Journal Article %J Scientific Reports %D 2023 %T Bioprospecting for industrially relevant exopolysaccharide-producing cyanobacteria under Portuguese simulated climate %A Cruz, José Diogo %A Delattre, Cédric %A Felpeto, Aldo Barreiro %A Pereira, Hugo %A Pierre, Guillaume %A Morais, João %A Petit, Emmanuel %A Silva, Joana %A Azevedo, Joana %A Elboutachfaiti, Redouan %A Maia, Inês B. %A Dubessay, Pascal %A Michaud, Philippe %A Vasconcelos, Vitor %K Biochemistry %K Biotechnology %K Microbiology %K rcc2380 %X Cyanobacterial exopolysaccharides (EPS) are potential candidates for the production of sustainable biopolymers. Although the bioactive and physicochemical properties of cyanobacterial-based EPS are attractive, their commercial exploitation is limited by the high production costs. Bioprospecting and characterizing novel EPS-producing strains for industrially relevant conditions is key to facilitate their implementation in various biotechnological applications and fields. In the present work, we selected twenty-five Portuguese cyanobacterial strains from a diverse taxonomic range (including some genera studied for the first time) to be grown in diel light and temperature, simulating the Portuguese climate conditions, and evaluated their growth performance and proximal composition of macronutrients. Synechocystis and Cyanobium genera, from marine and freshwater origin, were highlighted as fast-growing (0.1–0.2 g L−1 day−1) with distinct biomass composition. Synechocystis sp. LEGE 07367 and Chroococcales cyanobacterium LEGE 19970, showed a production of 0.3 and 0.4 g L−1 of released polysaccharides (RPS). These were found to be glucan-based polymers with high molecular weight and a low number of monosaccharides than usually reported for cyanobacterial EPS. In addition, the absence of known cyanotoxins in these two RPS producers was also confirmed. This work provides the initial steps for the development of cyanobacterial EPS bioprocesses under the Portuguese climate. %B Scientific Reports %V 13 %P 13561 %G eng %U https://www.nature.com/articles/s41598-023-40542-6 %R 10.1038/s41598-023-40542-6 %0 Journal Article %J Algal Research %D 2023 %T Fine-tuning the flavor of Tetraselmis chuii by modifying nitrogen supply %A Coleman, Bert %A Van Poucke, Christof %A Dewitte, Bavo %A Casciaro, Valentina %A Moerdijk-Poortvliet, Tanja %A Muylaert, Koenraad %A Robbens, Johan %K Microalgae %K Nitrogen starvation %K RCC128 %K Sensory evaluation %K Umami %K Volatile organic compounds %X Dried Tetraselmis chuii biomass has potential as flavoring agent for the development of plant-based seafood alternatives because of its seafood-like aroma and strong umami taste. Depending on the cultivation conditions, microalgae can adapt their metabolism, resulting in a change in biochemical composition. The aim of this study was to assess if the flavor of T. chuii could be modified by changing the nitrogen (N) supply in the cultivation medium in order to maximize the potential of T. chuii as flavoring agent. The sensory evaluation by a trained panel showed that the T. chuii biomass obtained from N starved cultivation conditions (N-deplete) is characterized by a significantly stronger odor intensity and earthy-like off-odor compared to T. chuii biomass obtained from N sufficient cultivation conditions (N-replete). The analysis of volatile organic compounds (VOCs) using SPME-GC–MS showed that these odor features of N-deplete biomass are attributed to an increased formation of odor-active VOCs including 2,3-butanedione, 3-methylbutanal, 3-methylbutanol and sulfur-containing dimethyl sulfide and dimethyl disulfide. In contrast, the T. chuii N-replete biomass possessed a significantly stronger taste intensity, umami and salty taste compared to the T. chuii N-deplete biomass. The higher umami is attributed to the significantly higher free glutamic acid (Glu) and adenosine monophosphate (AMP) concentrations in N-replete biomass compared to N-deplete biomass. This study illustrates that flavor and palatability of microalgae biomass is strongly affected by cultivating conditions and modifying these conditions can be an important tool in the development of plant-based seafood alternatives. %B Algal Research %P 103208 %G eng %U https://www.sciencedirect.com/science/article/pii/S2211926423002412 %R 10.1016/j.algal.2023.103208 %0 Journal Article %J Journal of Experimental Botany %D 2023 %T Genetic and physiological responses to light quality in a deep ocean ecotype of Ostreococcus, an ecologically important photosynthetic picoeukaryote %A Sands, Elizabeth %A Davies, Sian %A Puxty, Richard John %A Vergé, Valérie %A Bouget, François-Yves %A Scanlan, David John %A Carré, Isabelle Alice %K Rcc141 %K RCC4221 %K RCC745 %K RCC809 %X Abstract Phytoplankton are exposed to dramatic variations in light quality when cells are carried by upwelling or downwelling currents or encounter sediment. We investigated the potential impact of light quality changes in Ostreococcus, a key marine photosynthetic picoeukaryote, by analysing changes in its transcriptome, pigment content and photophysiology after acclimation to monochromatic red, green or blue light. The clade B species RCC809, isolated from the deep euphotic zone of the tropical Atlantic Ocean, responded to blue light by accelerating cell division at the expense of storage reserves and by increasing the relative level of blue-light absorbing pigments. RCC809 responded to red and green light by increasing its potential for photoprotection. In contrast, the clade A species OTTH0595, which originates from a shallow water environment, showed no difference in photosynthetic properties and minor differences in carotenoid contents between light qualities. This was associated with the loss of candidate lightquality responsive promoter motifs identified in RCC809 genes. These results demonstrate that light quality can have a major influence on the physiology of eukaryotic phytoplankton and suggest that different light quality environments can drive selection for diverse patterns of responsiveness and environmental niche partitioning. %B Journal of Experimental Botany %P erad347 %G eng %U https://academic.oup.com/jxb/advance-article/doi/10.1093/jxb/erad347/7258950 %R 10.1093/jxb/erad347 %0 Generic %D 2023 %T An INDEL genomic approach to explore population diversity of phytoplankton : \textit{Bathycoccus , a case study %A Devic, Martine %A Mariac, Cédric %A Vergé, Valérie %A Schatt, Philipe %A Dennu, Louis %A Lozano, Jean-Claude %A Bouget, François-Yves %A Sabot, François %K RCC1613 %K RCC1615 %K RCC1868 %K RCC4222 %K RCC4752 %K RCC5417 %K RCC685 %X Abstract Although metabarcoding has generated large dataset on world-wide phytoplankton species diversity, little is known about the intraspecies diversity underlying adaptation to environmental niches. To gain insight into population diversity, a novel INDEL based method was developed on Bathycoccus prasinos . Oxford Nanopore Technology (ONT) sequencing was first used to characterise structural variants (SV) among the genomes of Bathycoccus sampled from geographically distinct regions in the world ocean. Markers derived from INDEL were validated by PCR and sequencing in the world-wide strains. These markers were then used to genotype 55 Bathycoccus strains isolated during the winter bloom 2018-2019 in the bay of Banyuls-sur-Mer. With five markers, eight Multi Loci Genotypes (MLG) were determined, two of which represented 53% and 29% of the isolates. Physiological studies confirmed that isolates are phenotypically different, cells isolated in February growing better at low temperature than those isolated in December and January. When tested directly on environmental samples, two diversity markers showed a similar allele frequency in sea water as in individual Bathycoccus strains isolated at the same period. We conclude that these markers constitute a resource to identify the most abundant variant alleles in a given bloom. A follow-up on three consecutive blooms revealed differences in allele abundance during the course of a bloom, particularly at initiation and between years. This INDEL-based genotyping constitutes a new methodological approach that may be used to assess the population structure and diversity of other species. %I Ecology %G eng %U http://biorxiv.org/lookup/doi/10.1101/2023.02.09.527951 %9 preprint %R 10.1101/2023.02.09.527951 %0 Journal Article %J European Journal of Taxonomy %D 2023 %T New species of Pavlovophyceae (Haptophyta) and revision of the genera Exanthemachrysis, Rebecca and Pavlova %A Veron, Benoit %A Rougier, Etienne %A Taylor, Anthony %A Goux, Didier %K habitats %K haptophytes %K new species %K phytoplankton %K pyrenoid %K RCC1528 %K RCC1541 %X The justification of the 4 genera that currently compose the class Pavlovophyceae is based on a low number of species and a relative paucity of available, traceable and referenced cultures. Previous integrative phylogeny work revealed strains that can refine and strengthen our knowledge of the genera in the class. The application of multiple light and electron microscopy techniques allowed us to prioritize the cytomorphological characters (pyrenoid, thylakoid, stigma, knob-scales, life stage / life cycle) used for the taxonomy of these algae and to describe two new species: Exanthemachrysis fresneliae Véron sp. nov. and Rebecca billardiae Véron sp. nov. Consequently, revisions of the two genera Exanthemachrysis Lepailleur emend. Véron and Rebecca Green emend. Véron were made. In addition, the genus Pavlova Butcher emend Véron is revised in the light of these characters. Particular emphasis is placed on the life stages and habitat of the species. %B European Journal of Taxonomy %V 861 %P 21–47 %8 mar %G eng %U https://europeanjournaloftaxonomy.eu/index.php/ejt/article/view/2063 %R 10.5852/ejt.2023.861.2063 %0 Generic %D 2023 %T Novel dimethylsulfoniopropionate biosynthesis enzymes in diverse marine bacteria, cyanobacteria and abundant algae %A Wang, Jinyan %A Zhou, Shun %A Curson, Andrew %A Vieira, Ana %A Walsham, Keanu %A Monaco, Serena %A Li, Chun-Yang %A Rivera, Peter Paolo %A Wang, Xiao-Di %A Hanwell, Libby %A Zhu, Xiao-Yu %A Leão, Pedro %A Lea-Smith, David J. %A Zhang, Yuzhong %A Zhang, Xiaohua %A Todd, Jonathan %K RCC100 %K RCC2956 %K RCC4094 %K RCC4422 %K RCC6172 %X Abstract Dimethylsulfoniopropionate (DMSP) is an abundant marine organosulfur compound[1] with roles in stress protection[2, 3], chemotaxis[4], nutrient and sulfur cycling[5] and, potentially, climate regulation[6, 7]. Marine algae and bacteria are considered significant DMSP producers, but many diverse representatives lack known DMSP synthesis genes/enzymes[8, 9]. Here, new DMSP biosynthesis enzymes were identified that considerably increase the number and diversity of potential DMSP-producing organisms, inferring new and significant global DMSP producers. A novel bifunctional DMSP biosynthesis enzyme, DsyGD, identified in the rhizobacterium Gynuella sunshinyii, produces DMSP at levels higher than any other bacterium from methylthiohydroxybutyrate (MTHB) via an N-terminal MTHB S-methyltransferase domain (termed DsyG) and a C-terminal dimethylsulfoniohydroxybutyrate (DMSHB) decarboxylase domain (termed DsyD, which is the first reported enzyme with this activity). DsyGD is also found in some filamentous cyanobacteria, not previously known to produce DMSP. Regulation of DMSP production and dsyGD transcription was consistent with their role in osmoprotection. Indeed, cloned dsyGD conferred osmotolerance to bacteria deficient in osmolyte production, something not previously demonstrated for any known DMSP synthesis gene, and which could be exploited for biotechnology e.g., engineering salt tolerance. DsyGD characterisation led to identification of phylogenetically distinct DsyG-like proteins, termed DSYE, with MTHB S-methyltransferase activity, in diverse and environmentally abundant Chlorophyta, Chlorachniophyta, Ochraphyta, Haptophyta and Bacillariophyta algae. These algae comprise a mix of low, high and previously unknown DMSP producers[10]. Algae containing DSYE, particularly bloom-forming Pelagophyceae species, which we showed to accumulate medium-high intracellular DMSP levels, were globally more abundant DMSP producers than Haptophyta, Dinophyta and Bacillariophyta with DSYB and/or TpMMT. This highlights the potential importance of Pelagophyceae and other DSYE containing algae in global DMSP production and sulfur cycling. %I In Review %8 mar %G eng %U https://www.researchsquare.com/article/rs-2678769/v1 %9 preprint %R 10.21203/rs.3.rs-2678769/v1 %0 Generic %D 2023 %T Population dynamics of the cosmopolitan eukaryotic picophytoplankton Bathycoccus during seasonal blooms in the bay of Banyuls sur Mer (North Western Mediterranean sea) %A Devic, Martine %A Mariac, Cédric %A Vergé, Valérie %A Schatt, Philipe %A Dennu, Louis %A Lozano, Jean-Claude %A Bouget, François-Yves %A Sabot, François %K RCC1613 %K RCC1615 %K RCC1868 %K RCC4222 %K RCC4752 %K RCC5417 %K RCC685 %X Abstract Although Bathycoccus is one of the most abundant picophytoplankton, little is known about the genetic diversity underlying its adaptation to ecological niches. In this study, the diversity of Bathycoccus populations during their annual bloom in the Mediterranean bay of Banyuls France was assessed by an INDEL based approach. Oxford Nanopore Technology (ONT) was used to characterise structural variants (SV) among the genomes of Bathycoccus sampled from geographically distinct regions in the world ocean. Markers derived from INDEL were validated by PCR and sequencing in the world-wide strains. These markers were then used to genotype 55 Bathycoccus strains isolated during the winter bloom 2018-2019 in Banyuls. With five markers, eight Multi Loci Genotypes (MLG) were determined, two of which represented 53% and 29% of the isolates. Physiological studies confirmed that isolates are phenotypically different, cells isolated in February growing better at low temperature than those isolated in December. When tested on environmental samples, two diversity markers showed a similar allele frequency in sea water as in individual Bathycoccus strains isolated at the same period. We conclude that these markers constitute a resource to identify the most abundant variant alleles in a given bloom. A follow-up on three consecutive blooms revealed differences in allele abundance during the course of a bloom, particularly at initiation, and between years. In addition to Bathycoccus prasinos , two other species of Bathycoccus were identified including the recently described species B. calidus and a novel species B. catiminus , suggesting that species diversity of the genus Bathycoccus may be underestimated. %I BioRxiv %G eng %U http://biorxiv.org/lookup/doi/10.1101/2023.02.09.527951 %9 preprint %R 10.1101/2023.02.09.527951 %0 Journal Article %J Scientific Reports %D 2023 %T Unexpected silicon localization in calcium carbonate exoskeleton of cultured and fossil coccolithophores %A Bordiga, M. %A Lupi, C. %A Langer, G. %A Gianoncelli, A. %A Birarda, G. %A Pollastri, S. %A Bonanni, V. %A Bedolla, D. E. %A Vaccari, L. %A Gariani, G. %A Cerino, F. %A Cabrini, M. %A Beran, A. %A Zuccotti, M. %A Fiorentino, G. %A Zanoni, M. %A Garagna, S. %A Cobianchi, M. %A Di Giulio, A. %K Biogeochemistry %K Marine biology %K Palaeontology %K RCC1323 %X Coccolithophores, marine calcifying phytoplankton, are important primary producers impacting the global carbon cycle at different timescales. Their biomineral structures, the calcite containing coccoliths, are among the most elaborate hard parts of any organism. Understanding the morphogenesis of coccoliths is not only relevant in the context of coccolithophore eco-physiology but will also inform biomineralization and crystal design research more generally. The recent discovery of a silicon (Si) requirement for crystal shaping in some coccolithophores has opened up a new avenue of biomineralization research. In order to develop a mechanistic understanding of the role of Si, the presence and localization of this chemical element in coccoliths needs to be known. Here, we document for the first time the uneven Si distribution in Helicosphaera carteri coccoliths through three synchrotron-based techniques employing X-ray Fluorescence and Infrared Spectromicroscopy. The enrichment of Si in specific areas of the coccoliths point to a targeted role of this element in the coccolith formation. Our findings mark a key step in biomineralization research because it opens the door for a detailed mechanistic understanding of the role Si plays in shaping coccolith crystals. %B Scientific Reports %V 13 %P 7417 %8 may %G eng %U https://www.nature.com/articles/s41598-023-34003-3 %R 10.1038/s41598-023-34003-3 %0 Journal Article %J Current Biology %D 2023 %T The V-type ATPase enhances photosynthesis in marine phytoplankton and further links phagocytosis to symbiogenesis %A Yee, Daniel P. %A Samo, Ty J. %A Abbriano, Raffaela M. %A Shimasaki, Bethany %A Vernet, Maria %A Mayali, Xavier %A Weber, Peter K. %A Mitchell, B. Greg %A Hildebrand, Mark %A Decelle, Johan %A Tresguerres, Martin %K RCC3387 %X Diatoms, dinoflagellates, and coccolithophores are dominant groups of marine eukaryotic phytoplankton that are collectively responsible for the majority of primary production in the ocean.1 These phytoplankton contain additional intracellular membranes around their chloroplasts, which are derived from ancestral engulfment of red microalgae by unicellular heterotrophic eukaryotes that led to secondary and tertiary endosymbiosis.2 However, the selectable evolutionary advantage of these membranes and the physiological significance for extant phytoplankton remain poorly understood. Since intracellular digestive vacuoles are ubiquitously acidified by V-type H+-ATPase (VHA),3 proton pumps were proposed to acidify the microenvironment around secondary chloroplasts to promote the dehydration of dissolved inorganic carbon (DIC) into CO2, thus enhancing photosynthesis.4,5 We report that VHA is localized around the chloroplasts of centric diatoms and that VHA significantly contributes to their photosynthesis across a wide range of oceanic irradiances. Similar results in a pennate diatom, dinoflagellate, and coccolithophore, but not green or red microalgae, imply the co-option of phagocytic VHA activity into a carbon-concentrating mechanism (CCM) is common to secondary endosymbiotic phytoplankton. Furthermore, analogous mechanisms in extant photosymbiotic marine invertebrates6–8 provide functional evidence for an adaptive advantage throughout the transition from endosymbiosis to symbiogenesis. Based on the contribution of diatoms to ocean biogeochemical cycles, VHA-mediated enhancement of photosynthesis contributes at least 3.5 Gtons of fixed carbon per year (or 7% of primary production in the ocean), providing an example of a symbiosis-derived evolutionary innovation with global environmental implications. %B Current Biology %P S0960982223006152 %8 may %G eng %U https://linkinghub.elsevier.com/retrieve/pii/S0960982223006152 %R 10.1016/j.cub.2023.05.020 %0 Journal Article %J Marine Micropaleontology %D 2022 %T Coccolith size rules – What controls the size of coccoliths during coccolithogenesis? %A Suchéras-Marx, Baptiste %A Viseur, Sophie %A Walker, Charlotte E. %A Beaufort, Luc %A Probert, Ian %A Bolton, Clara %K Biometry %K coccolith %K coccolithophore %K life cycle %K RCC1216 %K Size variation %X Heterococcoliths are calcite platelets produced inside diploid coccolithophore cells and extruded to form a covering on the cell surface called a coccosphere. The size of coccoliths is an important parameter sometimes used to identify species, and it is observed to be influenced in extant species by abiotic parameters (e.g., CO2, light). However, the variable distribution of coccolith sizes occurring within a single coccosphere questions the mechanisms controlling coccolith size. A relationship between cell/coccosphere size and mean coccolith size was previously identified, called the “coccolithophore size rules”. In this study, we query the mechanisms controlling the size of a coccolith during coccolithogenesis. A culture experiment on Gephyrocapsa huxleyi strain RCC1216 shows that coccolithogenesis occurs during the cell growth G1 interphase and newly produced coccoliths get bigger as the cell grows. These observations provide parameters for the development of two numerical models used to simulate the coccolith size distribution within a coccolithophore population. Neither model can accurately reproduce an empirical monoclonal coccolith size distribution, indicating that additional factors influence coccolith size. According to our results, coccolith size is only clearly related to cell size at the time of its formation. We confirm that application of the coccolithophore size rules model should be limited to inferring average cell dimensions from (fossil) coccolith biometry, and that comparisons are valid only in multipopulational studies. The coccolith size rule model – the constraining effect of coccolith production during G1 interphase cell growth on coccolith size – proposed here is applicable only for some placolith-forming species. %B Marine Micropaleontology %V 170 %P 102080 %G eng %U https://www.sciencedirect.com/science/article/pii/S0377839821001213 %R 10.1016/j.marmicro.2021.102080 %0 Journal Article %J Microbial Ecology %D 2022 %T High-CO2 Levels Rather than Acidification Restrict Emiliania huxleyi Growth and Performance %A Vázquez, Víctor %A León, Pablo %A Gordillo, Francisco J. L. %A Jiménez, Carlos %A Concepción, Iñiguez %A Mackenzie, Kevin %A Bresnan, Eileen %A Segovia, María %K Calcification %K coccolithophores %K Emiliania huxleyi %K Ocean acidification %K pCO2 %K Photochemistry %K phytoplankton %K rcc1226 %K Stress %X The coccolithophore Emiliania huxleyi shows a variety of responses to ocean acidification (OA) and to high-CO2 concentrations, but there is still controversy on differentiating between these two factors when using different strains and culture methods. A heavily calcified type A strain isolated from the Norwegian Sea was selected and batch cultured in order to understand whether acclimation to OA was mediated mainly by CO2 or H+, and how it impacted cell growth performance, calcification, and physiological stress management. Emiliania huxleyi responded differently to each acidification method. CO2-enriched aeration (1200 µatm, pH 7.62) induced a negative effect on the cells when compared to acidification caused by decreasing pH alone (pH 7.60). The growth rates of the coccolithophore were more negatively affected by high pCO2 than by low pH without CO2 enrichment with respect to the control (400 µatm, pH 8.1). High CO2 also affected cell viability and promoted the accumulation of reactive oxygen species (ROS), which was not observed under low pH. This suggests a possible metabolic imbalance induced by high CO2 alone. In contrast, the affinity for carbon uptake was negatively affected by both low pH and high CO2. Photochemistry was only marginally affected by either acidification method when analysed by PAM fluorometry. The POC and PIC cellular quotas and the PIC:POC ratio shifted along the different phases of the cultures; consequently, calcification did not follow the same pattern observed in cell stress and growth performance. Specifically, acidification by HCl addition caused a higher proportion of severely deformed coccoliths, than CO2 enrichment. These results highlight the capacity of CO2 rather than acidification itself to generate metabolic stress, not reducing calcification. %B Microbial Ecology %G eng %U https://doi.org/10.1007/s00248-022-02035-3 %R 10.1007/s00248-022-02035-3 %0 Journal Article %J Comptes Rendus. Biologies %D 2022 %T Light-driven processes: key players of the functional biodiversity in microalgae %A Falciatore, Angela %A Bailleul, Benjamin %A Boulouis, Alix %A Bouly, Jean-Pierre %A Bujaldon, Sandrine %A Cheminant-Navarro, Soizic %A Choquet, Yves %A Vitry, Catherine de %A Eberhard, Stephan %A Jaubert, Marianne %A Kuras, Richard %A Lafontaine, Ingrid %A Landier, Sophie %A Selles, Julien %A Vallon, Olivier %A Wostrikoff, Katia %B Comptes Rendus. Biologies %V 345 %P 1–24 %G eng %U https://comptes-rendus.academie-sciences.fr/biologies/articles/10.5802/crbiol.80/ %R 10.5802/crbiol.80 %0 Journal Article %J Molecular Phylogenetics and Evolution %D 2022 %T Providing a phylogenetic framework for trait-based analyses in brown algae: Phylogenomic tree inferred from 32 nuclear protein-coding sequences %A Akita, Shingo %A Vieira, Christophe %A Hanyuda, Takeaki %A Rousseau, Florence %A Cruaud, Corinne %A Couloux, Arnaud %A Heesch, Svenja %A Cock, J. Mark %A Kawai, Hiroshi %K Ectocarpales %K genomics %K Heterokontophytes %K Phaeoexplorer %K Phaeophyceae %K RCC4962 %K RCC7086 %K RCC7088 %K RCC7090 %K RCC7092 %K RCC7094 %K RCC7096 %K RCC7098 %K RCC7101 %K RCC7104 %K RCC7107 %K RCC7108 %K RCC7109 %K RCC7112 %K RCC7115 %K RCC7116 %K RCC7117 %K RCC7120 %K RCC7123 %K RCC7124 %K RCC7125 %K RCC7127 %K RCC7129 %K RCC7131 %K RCC7134 %K RCC7137 %K RCC7138 %K RCC7139 %K stramenopiles %X In the study of the evolution of biological complexity, a reliable phylogenetic framework is needed. Many attempts have been made to resolve phylogenetic relationships between higher groups (i.e., interordinal) of brown algae (Phaeophyceae) based on molecular evidence, but most of these relationships remain unclear. Analyses based on small multi-gene data (including chloroplast, mitochondrial and nuclear sequences) have yielded inconclusive and sometimes contradictory results. To address this problem, we have analyzed 32 nuclear protein-coding sequences in 39 Phaeophycean species belonging to eight orders. The resulting nuclear-based phylogenomic trees provide virtually full support for the phylogenetic relationships within the studied taxa, with few exceptions. The relationships largely confirm phylogenetic trees based on nuclear, chloroplast and mitochondrial sequences, except for the placement of the Sphacelariales with weak bootstrap support. Our study indicates that nuclear protein-coding sequences provide significant support to conclusively resolve phylogenetic relationships among Phaeophyceae, and may be a powerful approach to fully resolve interordinal relationships with increased taxon sampling. %B Molecular Phylogenetics and Evolution %V 168 %P 107408 %8 mar %G eng %U https://www.sciencedirect.com/science/article/pii/S1055790322000215 %R 10.1016/j.ympev.2022.107408 %0 Journal Article %J Marine Drugs %D 2022 %T Scale-Up to Pilot of a Non-Axenic Culture of Thraustochytrids Using Digestate from Methanization as Nitrogen Source %A de la Broise, Denis %A Ventura, Mariana %A Chauchat, Luc %A Guerreiro, Maurean %A Michez, Teo %A Vinet, Thibaud %A Gautron, Nicolas %A Le Grand, Fabienne %A Bideau, Antoine %A Goïc, Nelly Le %A Bidault, Adeline %A Lambert, Christophe %A Soudant, Philippe %K RCC893 %X The production of non-fish based docosahexaenoic acid (DHA) for feed and food has become a critical need in our global context of over-fishing. The industrial-scale production of DHA–rich Thraustochytrids could be an alternative, if costs turned out to be competitive. In order to reduce production costs, this study addresses the feasibility of the non-axenic (non-sterile) cultivation of Aurantiochytrium mangrovei on industrial substrates (as nitrogen and mineral sources and glucose syrup as carbon and energy sources), and its scale-up from laboratory (250 mL) to 500 L cultures. Pilot-scale reactors were airlift cylinders. Batch and fed-batch cultures were tested. Cultures over 38 to 62 h achieved a dry cell weight productivity of 3.3 to 5.5 g.L−1.day−1, and a substrate to biomass yield of up to 0.3. DHA productivity ranged from 10 to 0.18 mg.L−1.day−1. Biomass productivity appears linearly related to oxygen transfer rate. Bacterial contamination of cultures was low enough to avoid impacts on fatty acid composition of the biomass. A specific work on microbial risks assessment (in supplementary files) showed that the biomass can be securely used as feed. However, to date, there is a law void in EU legislation regarding the recycling of nitrogen from digestate from animal waste for microalgae biomass and its usage in animal feed. Overall, the proposed process appears similar to the industrial yeast production process (non-axenic heterotrophic process, dissolved oxygen supply limiting growth, similar cell size). Such similarity could help in further industrial developments. %B Marine Drugs %V 20 %P 499 %8 aug %G eng %U https://www.mdpi.com/1660-3397/20/8/499 %R 10.3390/md20080499 %0 Journal Article %J Frontiers in Plant Science %D 2021 %T Altitudinal Zonation of Green Algae Biodiversity in the French Alps %A Stewart, Adeline %A Rioux, Delphine %A Boyer, Fréderic %A Gielly, Ludovic %A Pompanon, François %A Saillard, Amélie %A Thuiller, Wilfried %A Valay, Jean-Gabriel %A Maréchal, Éric %A Coissac, Eric %K rcc %K RCC1055 %K RCC130 %K RCC1563 %K RCC2501 %K RCC2960 %K RCC3402 %K RCC443 %K RCC4743 %K RCC537 %K RCC581 %K RCC6 %K RCC7 %K RCC891 %X Mountain environments are marked by an altitudinal zonation of habitat types. They are home to a multitude of terrestrial green algae, who have to cope with abiotic conditions specific to high elevation, e.g., high UV irradiance, alternating desiccation, rain and snow precipitations, extreme diurnal variations in temperature and chronic scarceness of nutrients. Even though photosynthetic green algae are primary producers colonizing open areas and potential markers of climate change, their overall biodiversity in the Alps has been poorly studied so far, in particular in soil, where algae have been shown to be key components of microbial communities. Here, we investigated whether the spatial distribution of green algae followed the altitudinal zonation of the Alps, based on the assumption that algae settle in their preferred habitats under the pressure of parameters correlated with elevation. We did so by focusing on selected representative elevational gradients at distant locations in the French Alps, where soil samples were collected at different depths. Soil was considered as either a potential natural habitat or temporary reservoir of algae. We showed that algal DNA represented a relatively low proportion of the overall eukaryotic diversity as measured by a universal Eukaryote marker. We designed two novel green algae metabarcoding markers to amplify the Chlorophyta phylum and its Chlorophyceae class, respectively. Using our newly developed markers, we showed that elevation was a strong correlate of species and genus level distribution. Altitudinal zonation was thus determined for about fifty species, with proposed accessions in reference databases. In particular, Planophila laetevirens and Bracteococcus ruber related species as well as the snow alga Sanguina genus were only found in soil starting at 2,000 m above sea level. Analysis of environmental and bioclimatic factors highlighted the importance of pH and nitrogen/carbon ratios in the vertical distribution in soil. Capacity to grow heterotrophically may determine the Trebouxiophyceae over Chlorophyceae ratio. The intensity of freezing events (freezing degree days), proved also determinant in Chlorophyceae distribution. Guidelines are discussed for future, more robust and precise analyses of environmental algal DNA in mountain ecosystems and address green algae species distribution and dynamics in response to environmental changes. %B Frontiers in Plant Science %V 12 %P 1066 %G eng %U https://www.frontiersin.org/article/10.3389/fpls.2021.679428 %R 10.3389/fpls.2021.679428 %0 Journal Article %J Scientific Reports %D 2021 %T Annual phytoplankton dynamics in coastal waters from fildes bay, western antarctic peninsula %A Trefault, Nicole %A de la Iglesia, Rodrigo %A Moreno-Pino, Mario %A Lopes dos Santos, Adriana %A Gérikas Ribeiro, Catherine %A Parada-Pozo, Génesis %A Cristi, Antonia %A Marie, Dominique %A Vaulot, Daniel %K RCC2265 %K RCC2289 %K RCC4582 %K RCC4586 %K RCC5152 %X Year-round reports of phytoplankton dynamics in the West Antarctic Peninsula are rare and mainly limited to microscopy and/or pigment-based studies. We analyzed the phytoplankton community from coastal waters of Fildes Bay in the West Antarctic Peninsula between January 2014 and 2015 using metabarcoding of the nuclear and plastidial 18/16S rRNA gene from both size-fractionated and flow cytometry sorted samples. Overall 14 classes of photosynthetic eukaryotes were present in our samples with the following dominating: Bacillariophyta (diatoms), Pelagophyceae and Dictyochophyceae for division Ochrophyta, Mamiellophyceae and Pyramimonadophyceae for division Chlorophyta, Haptophyta and Cryptophyta. Each metabarcoding approach yielded a different image of the phytoplankton community with for example Prymnesiophyceae more prevalent in plastidial metabarcodes and Mamiellophyceae in nuclear ones. Diatoms were dominant in the larger size fractions and during summer, while Prymnesiophyceae and Cryptophyceae were dominant in colder seasons. Pelagophyceae were particularly abundant towards the end of autumn (May). In addition of Micromonas polaris and Micromonas sp. clade B3, both previously reported in Arctic waters, we detected a new Micromonas 18S rRNA sequence signature, close to, but clearly distinct from M. polaris , which potentially represents a new clade specific of the Antarctic. These results highlight the need for complementary strategies as well as the importance of year-round monitoring for a comprehensive description of phytoplankton communities in Antarctic coastal waters. %B Scientific Reports %V 11 %P 1368 %8 dec %G eng %U http://biorxiv.org/content/early/2020/10/27/2020.10.27.356600.abstract http://www.nature.com/articles/s41598-020-80568-8 %R 10.1038/s41598-020-80568-8 %0 Journal Article %J Environmental Science: Water Research & Technology %D 2021 %T Determination of the efficiency of filtration of cultures from microalgae and bacteria using hollow fiber filters %A Robla, J. %A García-Hierrro, J. %A Alguacil, F. J. %A Dittami, S. M. %A Marie, D. %A Villa, E. %A Deragon, E. %A Guillebault, D. %A Mengs, G. %A Medlin, L. K. %K rcc %K RCC1507 %X The most important question in sampling is “Is the sample representative of the target population?” This question is necessary to understand how valid the sample taken is to the original population and if generalizations can be made from the sample. Samples taken for water quality measurement range from 1 mL for bacterial contamination to 100 mL or up to 1000 L for protozoan parasites. With larger samples taken, the confidence in detecting rare events increases dramatically. Here we illustrate that hollow fiber filters as routinely used for kidney dialysis can be adapted for environmental use. The filters retain all organisms down to viral particles and organic matter above 70 kDA, the molecular cutoff for urea, one of the waste products removed in kidney dialysis. With these filters, 50 liters of water can be filtered in about 90 minutes. Backflush of the filters recovers viable cells with minimal cell lysis that can be processed downstream for molecular analysis. Recovery rates were as high as 89% and 75% for phytoplankton and bacteria, respectively. %B Environmental Science: Water Research & Technology %V 7 %P 1230–1239 %8 jul %G eng %U https://pubs.rsc.org/en/content/articlelanding/2021/ew/d0ew00927j %R 10.1039/D0EW00927J %0 Journal Article %J Genome Biology and Evolution %D 2021 %T Evolutionary Genomics of Sex-Related Chromosomes at the Base of the Green Lineage %A Benites, Luis Felipe %A Bucchini, François %A Sanchez-Brosseau, Sophie %A Grimsley, Nigel %A Vandepoele, Klaas %A Piganeau, Gwenael %E Wolfe, Kenneth %K RCC1105 %K RCC1115 %K RCC2590 %K RCC299 %K rcc3401 %K RCC4221 %K RCC809 %K RCC834 %X Although sex is now accepted as a ubiquitous and ancestral feature of eukaryotes, direct observation of sex is still lacking in most unicellular eukaryotic lineages. Evidence of sex is frequently indirect and inferred from the identification of genes involved in meiosis from whole genome data and/or the detection of recombination signatures from genetic diversity in natural populations. In haploid unicellular eukaryotes, sex-related chromosomes are named mating-type (MTs) chromosomes and generally carry large genomic regions where recombination is suppressed. These regions have been characterized in Fungi and Chlorophyta and determine gamete compatibility and fusion. Two candidate MTþ and MTÀ alleles, spanning 450–650 kb, have recently been described in Ostreococcus tauri, a marine phytoplanktonic alga from the Mamiellophyceae class, an early diverging branch in the green lineage. Here, we investigate the architecture and evolution of these candidate MTþ and MTÀ alleles. We analyzed the phylogenetic profile and GC content of MT gene families in eight different genomes whose divergence has been previously estimated at up to 640 Myr, and found evidence that the divergence of the two MT alleles predates speciation in the Ostreococcus genus. Phylogenetic profiles of MT transspecific polymorphisms in gametologs disclosed candidate MTs in two additional species, and possibly a third. These Mamiellales MT candidates are likely to be the oldest mating-type loci described to date, which makes them fascinating models to investigate the evolutionary mechanisms of haploid sex determination in eukaryotes. %B Genome Biology and Evolution %V 13 %P evab216 %G eng %U https://academic.oup.com/gbe/article/doi/10.1093/gbe/evab216/6380139 %R 10.1093/gbe/evab216 %0 Journal Article %J Protist %D 2021 %T Hemiselmis aquamarina sp . nov . (Cryptomonadales , Cryptophyceae), a cryptomonad with a novel phycobiliprotein type (Cr-PC 564) %A Magalhães, Karoline %A Lopes dos Santos, Adriana %A Vaulot, Daniel %A de Oliveira, Mariana Cabral %K RCC4102 %K RCC5634 %K to add %B Protist %V in press %G eng %U https://doi.org/10.1016/j.protis.2021.125832 %R 10.1016/j.protis.2021.125832 %0 Journal Article %J Journal of Phycology %D 2021 %T No evidence of Phago-mixotropy in Micromonas polaris (Mamiellophyceae), the Dominant Picophytoplankton Species in the Arctic %A Jimenez, Valeria %A Burns, John A. %A Le Gall, Florence %A Not, Fabrice %A Vaulot, Daniel %K Arctic %K Micromonas %K phago-mixotrophy %K phytoplankton %K rcc %K RCC21 %K RCC2288 %K RCC2306 %K RCC4298 %X In the Arctic Ocean, the small green alga Micromonas polaris dominates picophytoplankton during the summer months but is also present in winter. It has been previously hypothesized to be phago-mixotrophic (capable of bacteria ingestion) based on laboratory and field experiments. Prey uptake was analyzed in several M. polaris strains isolated from different regions and depths of the Arctic Ocean and in Ochromonas triangulata, a known phago-mixotroph used as a control. Measuring ingestion of either fluorescent beads or fluorescently labeled bacteria by flow cytometry, we found no evidence of phago-mixotrophy in any M. polaris strain while O. triangulata was ingesting both beads and bacteria. In addition, in silico predictions revealed that members of the genus Micromonas lack a genetic signature of phagocytotic capacity. %B Journal of Phycology %V 57 %P 435–446 %G eng %U https://onlinelibrary.wiley.com/doi/abs/10.1111/jpy.13125 %R 10.1111/jpy.13125 %0 Journal Article %J BMC Biology %D 2021 %T Rapid protein evolution, organellar reductions, and invasive intronic elements in the marine aerobic parasite dinoflagellate Amoebophrya spp. %A Farhat, Sarah %A Le, Phuong %A Kayal, Ehsan %A Noel, Benjamin %A Bigeard, Estelle %A Corre, Erwan %A Maumus, Florian %A Florent, Isabelle %A Alberti, Adriana %A Aury, Jean-Marc %A Barbeyron, Tristan %A Cai, Ruibo %A Silva, Corinne Da %A Istace, Benjamin %A Labadie, Karine %A Marie, Dominique %A Mercier, Jonathan %A Rukwavu, Tsinda %A Szymczak, Jeremy %A Tonon, Thierry %A Alves-de-Souza, Catharina %A Rouze, Pierre %A de Peer, Yves Van %A Wincker, Patrick %A Rombauts, Stephane %A Porcel, Betina M %A Guillou, Laure %K Dinoflagellate %K genome %K Introner elements %K Non-canonical introns %K parasite %K RCC4383 %K RCC4398 %B BMC Biology %P 1–21 %G eng %R 10.1186/s12915-020-00927-9 %0 Journal Article %J Environmental Microbiology %D 2021 %T Seasonal dynamics of natural Ostreococcus viral infection at the single cell level using VirusFISH %A Castillo, Yaiza M. %A Forn, Irene %A Yau, Sheree %A Morán, Xosé Anxelu G. %A Alonso-Sáez, Laura %A Arandia-Gorostidi, Néstor %A Vaqué, Dolors %A Sebastián, Marta %K RCC2590 %K RCC4221 %K RCC809 %X Ostreococcus is a cosmopolitan marine genus of phytoplankton found in mesotrophic and oligotrophic waters, and the smallest free-living eukaryotes known to date, with a cell diameter close to 1 μm. Ostreococcus has been extensively studied as a model system to investigate viral–host dynamics in culture, yet the impact of viruses in naturally occurring populations is largely unknown. Here, we used Virus Fluorescence in situ Hybridization (VirusFISH) to visualize and quantify viral-host dynamics in natural populations of Ostreococcus during a seasonal cycle in the central Cantabrian Sea (Southern Bay of Biscay). Ostreococcus were predominantly found during summer and autumn at surface and 50 m depth, in coastal, mid-shelf and shelf waters, representing up to 21% of the picoeukaryotic communities. Viral infection was only detected in surface waters, and its impact was variable but highest from May to July and November to December, when up to half of the population was infected. Metatranscriptomic data available from the mid-shelf station unveiled that the Ostreococcus population was dominated by the species O. lucimarinus. This work represents a proof of concept that the VirusFISH technique can be used to quantify the impact of viruses on targeted populations of key microbes from complex natural communities. This article is protected by copyright. All rights reserved. %B Environmental Microbiology %V n/a %G eng %U http://sfamjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1462-2920.15504 %R 10.1111/1462-2920.15504 %0 Journal Article %J bioRxiv %D 2021 %T Subcellular architecture and metabolic connection in the planktonic photosymbiosis between Collodaria (radiolarians) and their microalgae %A Decelle, Johan %A Veronesi, Giulia %A LeKieffre, Charlotte %A Gallet, Benoit %A Chevalier, Fabien %A Stryhanyuk, Hryhoriy %A Marro, Sophie %A Ravanel, Stéphane %A Tucoulou, Rémi %A Schieber, Nicole %A Finazzi, Giovanni %A Schwab, Yannick %A Musat, Niculina %X Photosymbiosis is widespread and ecologically important in the oceanic plankton but remains poorly studied. Here, we used multimodal subcellular imaging to investigate the photosymbiosis between colonial Collodaria and their microalga dinoflagellate (Brandtodinium) collected in surface seawaters. We showed that this symbiosis is a very dynamic system whereby symbionts interact with different host cells via extracellular vesicles within the “greenhouse-like” colony. 3D electron microscopy revealed that the volume of the photosynthetic apparatus (plastid and pyrenoid) of the microalgae increased in symbiosis compared to free-living while the mitochondria volume was similar. Stable isotope probing coupled with NanoSIMS showed that carbon and nitrogen were assimilated and stored in the symbiotic microalga in starch granules and purine crystals, respectively. Nitrogen was also allocated to the algal nucleus (nucleolus). After 3 hours, low 13C and 15N transfer was detected in the host Golgi. Metal mapping revealed that intracellular iron concentration was similar in free-living and symbiotic microalgae (ca 40 ppm) and two-fold higher in the host, whereas copper concentration increased in symbiotic microalgae (up to 6900 ppm) and was detected in the host cell and extracellular vesicles. Sulfur mapping also pinpointed the importance of this nutrient for the algal metabolism. This study, which revealed subcellular changes of the morphology and nutrient homeostasis in symbiotic microalgae, improves our understanding on the metabolism of this widespread and abundant oceanic symbiosis and paves the way for more studies to investigate the metabolites exchanged. %B bioRxiv %P 2021.03.13.435225 %G eng %U https://www.biorxiv.org/content/10.1101/2021.03.13.435225v1 %R 10.1101/2021.03.13.435225 %0 Generic %D 2021 %T The tropical coral Pocillopora acuta displays an unusual chromatin structure and shows histone H3 clipping plasticity upon bleaching %A Roquis, David %A Cosseau, Céline %A Raffalli, Kelly Brener %A Romans, Pascal %A Masanet, Patrick %A Mitta, Guillaume %A Grunau, Christoph %A Vidal-Dupiol, Jeremie %K chromatin structure %K Histone H3 clipping %K invertebrate epigenetics %K Pocillopora acuta %K Pocillopora damicornis %K rcc %K RCC4017 %X

Background: Pocillopora acuta is a hermatypic coral with strong ecological importance. Anthropogenic disturbances and global warming are major threats that can induce coral bleaching, the disruption of the mutualistic symbiosis between the coral host and its endosymbiotic algae. Previous works have shown that somaclonal colonies display different levels of survival depending on the environmental conditions they previously faced. Epigenetic mechanisms are good candidates to explain this phenomenon. However, almost no work had been published on the P. acuta epigenome, especially on histone modifications. In this study, we aim at providing the first insight into chromatin structure of this species. Methods: We aligned the amino acid sequence of P. acuta core histones with histone sequences from various phyla. We developed a centri-filtration on sucrose gradient to separate chromatin from the host and the symbiont. The presence of histone H3 protein and specific histone modifications were then detected by western blot performed on histone extraction done from bleached and healthy corals. Finally, micrococcal nuclease (MNase) digestions were undertaken to study nucleosomal organization. Results: The centri-filtration enabled coral chromatin isolation with less than 2% of contamination by endosymbiont material. Histone sequences alignments with other species show that P. acuta displays on average \textasciitilde90% of sequence similarities with mice and \textasciitilde96% with other corals. H3 detection by western blot showed that H3 is clipped in healthy corals while it appeared to be intact in bleached corals. MNase treatment failed to provide the usual mononucleosomal digestion, a feature shared with some cnidarian, but not all; suggesting an unusual chromatin structure. Conclusions: These results provide a first insight into the chromatin, nucleosome and histone structure of P. acuta . The unusual patterns highlighted in this study and partly shared with other cnidarian will need to be further studied to better understand its role in corals.

%I Wellcome Open Research %8 jul %G eng %U https://wellcomeopenresearch.org/articles/6-195 %R 10.12688/wellcomeopenres.17058.1 %0 Journal Article %J International Journal of Systematic and Evolutionary Microbiology %D 2021 %T Zobellia roscoffensis sp. nov. and Zobellia nedashkovskayae sp. nov., two flavobacteria from the epiphytic microbiota of the brown alga Ascophyllum nodosum, and emended description of the genus Zobellia %A Barbeyron, Tristan %A Thiébaud, Manon %A Le Duff, Nolwen %A Martin, Marjolaine %A Corre, Erwan %A Tanguy, Gwenn %A Vandenbol, Micheline %A Thomas, François %K RCC6906 %K RCC6907 %K RCC6908 %K RCC6909 %X Four marine bacterial strains were isolated from a thallus of the brown alga Ascophyllum nodosum collected in Roscoff, France. Cells were Gram-s­ tain-­negative, strictly aerobic, non-f­lagellated, gliding, rod-­shaped and grew optimally at 25–30 °C, at pH 7–8 and with 2–4 % NaCl. Phylogenetic analyses of their 16S rRNA gene sequences showed that the bacteria were affiliated to the genus Zobellia (family Flavobacteriaceae, phylum Bacteroidetes). The four strains exhibited 97.8–100 % 16S rRNA gene sequence similarity values among themselves, 97.9–99.1 % to the type strains of Zobellia amurskyensis KMM 3526T and Zobellia laminariae KMM 3676T, and less than 99 % to other species of the genus Zobellia. The DNA G+C content of the four strains ranged from 36.7 to 37.7 mol%. Average nucleotide identity and digital DNA–DNA hybridization calculations between the new strains and other members of the genus Zobellia resulted in values of 76.4–88.9 % and below 38.5 %, respectively. Phenotypic, phylogenetic and genomic analyses showed that the four strains are distinct from species of the genus Zobellia with validly published names. They represent two novel species of the genus Zobellia, for which the names Zobellia roscoffensis sp. nov. and Zobellia nedashkovskayae sp. nov. are proposed with Asnod1-­F08T (RCC6906T=KMM 6823T=CIP 111902T) and Asnod2-­B07-­BT (RCC6908T=KMM 6825T=CIP 111904T), respectively, as the type strains. %B International Journal of Systematic and Evolutionary Microbiology %V 71 %G eng %U https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/ijsem.0.004913 %R 10.1099/ijsem.0.004913 %0 Journal Article %J Elementa: Science of the Anthropocene %D 2020 %T Culturable diversity of Arctic phytoplankton during pack ice melting %A Ribeiro, Catherine Gérikas %A dos Santos, Adriana Lopes %A Gourvil, Priscillia %A Le Gall, Florence %A Marie, Dominique %A Tragin, Margot %A Probert, Ian %A Vaulot, Daniel %K RCC5197 %K RCC5198 %K RCC5199 %K RCC5200 %K RCC5201 %K RCC5202 %K RCC5203 %K RCC5204 %K RCC5205 %K RCC5206 %K RCC5207 %K RCC5208 %K RCC5209 %K RCC5210 %K RCC5211 %K RCC5212 %K RCC5213 %K RCC5214 %K RCC5215 %K RCC5216 %K RCC5217 %K RCC5218 %K RCC5219 %K RCC5220 %K RCC5221 %K RCC5222 %K RCC5223 %K RCC5224 %K RCC5225 %K RCC5226 %K RCC5227 %K RCC5228 %K RCC5229 %K RCC5230 %K RCC5231 %K RCC5232 %K RCC5233 %K RCC5234 %K RCC5235 %K RCC5236 %K RCC5237 %K RCC5238 %K RCC5239 %K RCC5240 %K RCC5241 %K RCC5242 %K RCC5243 %K RCC5244 %K RCC5245 %K RCC5246 %K RCC5247 %K RCC5248 %K RCC5249 %K RCC5250 %K RCC5251 %K RCC5252 %K RCC5253 %K RCC5254 %K RCC5255 %K RCC5256 %K RCC5257 %K RCC5258 %K RCC5259 %K RCC5260 %K RCC5261 %K RCC5262 %K RCC5263 %K RCC5264 %K RCC5265 %K RCC5266 %K RCC5267 %K RCC5268 %K RCC5269 %K RCC5270 %K RCC5271 %K RCC5272 %K RCC5273 %K RCC5274 %K RCC5275 %K RCC5276 %K RCC5277 %K RCC5278 %K RCC5279 %K RCC5280 %K RCC5281 %K RCC5282 %K RCC5283 %K RCC5284 %K RCC5285 %K RCC5286 %K RCC5287 %K RCC5288 %K RCC5289 %K RCC5290 %K RCC5291 %K RCC5292 %K RCC5293 %K RCC5294 %K RCC5295 %K RCC5296 %K RCC5297 %K RCC5298 %K RCC5299 %K RCC5300 %K RCC5301 %K RCC5302 %K RCC5303 %K RCC5304 %K RCC5305 %K RCC5306 %K RCC5307 %K RCC5308 %K RCC5309 %K RCC5310 %K RCC5311 %K RCC5312 %K RCC5313 %K RCC5314 %K RCC5315 %K RCC5316 %K RCC5317 %K RCC5318 %K RCC5319 %K RCC5320 %K RCC5321 %K RCC5322 %K RCC5323 %K RCC5324 %K RCC5325 %K RCC5326 %K RCC5327 %K RCC5328 %K RCC5329 %K RCC5330 %K RCC5331 %K RCC5332 %K RCC5333 %K RCC5334 %K RCC5335 %K RCC5336 %K RCC5337 %K RCC5338 %K RCC5339 %K RCC5340 %K RCC5341 %K RCC5342 %K RCC5343 %K RCC5344 %K RCC5345 %K RCC5346 %K RCC5347 %K RCC5348 %K RCC5349 %K RCC5350 %K RCC5351 %K RCC5352 %K RCC5353 %K RCC5354 %K RCC5355 %K RCC5356 %K RCC5357 %K RCC5358 %K RCC5359 %K RCC5360 %K RCC5361 %K RCC5362 %K RCC5363 %K RCC5364 %K RCC5365 %K RCC5366 %K RCC5367 %K RCC5368 %K RCC5369 %K RCC5370 %K RCC5371 %K RCC5372 %K RCC5373 %K RCC5374 %K RCC5375 %K RCC5376 %K RCC5377 %K RCC5378 %K RCC5379 %K RCC5380 %K RCC5381 %K RCC5382 %K RCC5383 %K RCC5384 %K RCC5385 %K RCC5386 %K RCC5387 %K RCC5388 %K RCC5389 %K RCC5390 %K RCC5391 %K RCC5392 %K RCC5393 %K RCC5394 %K RCC5395 %K RCC5396 %K RCC5397 %K RCC5398 %K RCC5399 %K RCC5400 %K RCC5401 %K RCC5402 %K RCC5403 %K RCC5404 %K RCC5405 %K RCC5406 %K RCC5407 %K RCC5408 %K RCC5409 %K RCC5410 %K RCC5411 %K RCC5412 %K RCC5413 %K RCC5414 %K RCC5415 %K RCC5416 %K RCC5417 %K RCC5418 %K RCC5419 %K RCC5420 %K RCC5421 %K RCC5422 %K RCC5423 %K RCC5424 %K RCC5425 %K RCC5426 %K RCC5427 %K RCC5428 %K RCC5429 %K RCC5430 %K RCC5431 %K RCC5432 %K RCC5433 %K RCC5434 %K RCC5435 %K RCC5436 %K RCC5437 %K RCC5438 %K RCC5439 %K RCC5440 %K RCC5441 %K RCC5442 %K RCC5443 %K RCC5444 %K RCC5445 %K RCC5446 %K RCC5447 %K RCC5448 %K RCC5449 %K RCC5450 %K RCC5451 %K RCC5452 %K RCC5453 %K RCC5454 %K RCC5455 %K RCC5456 %K RCC5457 %K RCC5458 %K RCC5459 %K RCC5460 %K RCC5461 %K RCC5462 %K RCC5463 %K RCC5464 %K RCC5465 %K RCC5466 %K RCC5467 %K RCC5468 %K RCC5469 %K RCC5470 %K RCC5471 %K RCC5472 %K RCC5473 %K RCC5474 %K RCC5475 %K RCC5476 %K RCC5477 %K RCC5478 %K RCC5479 %K RCC5480 %K RCC5481 %K RCC5482 %K RCC5483 %K RCC5484 %K RCC5485 %K RCC5486 %K RCC5487 %K RCC5488 %K RCC5489 %K RCC5490 %K RCC5491 %K RCC5492 %K RCC5493 %K RCC5494 %K RCC5495 %K RCC5496 %K RCC5497 %K RCC5498 %K RCC5499 %K RCC5500 %K RCC5501 %K RCC5502 %K RCC5503 %K RCC5504 %K RCC5505 %K RCC5506 %K RCC5507 %K RCC5508 %K RCC5509 %K RCC5510 %K RCC5511 %K RCC5512 %K RCC5513 %K RCC5514 %K RCC5515 %K RCC5516 %K RCC5517 %K RCC5518 %K RCC5519 %K RCC5520 %K RCC5521 %K RCC5522 %K RCC5523 %K RCC5524 %K RCC5525 %K RCC5526 %K RCC5527 %K RCC5528 %K RCC5529 %K RCC5530 %K RCC5531 %K RCC5532 %K RCC5533 %K RCC5534 %K RCC5535 %K RCC5536 %K RCC5537 %K RCC5538 %K RCC5539 %K RCC5540 %K RCC5541 %K RCC5542 %K RCC5543 %K RCC5544 %K RCC5545 %K RCC5546 %K RCC5547 %K RCC5548 %K RCC5549 %K RCC5550 %K RCC5551 %K RCC5552 %K RCC5553 %K RCC5554 %K RCC5555 %K RCC5556 %K RCC5557 %K RCC5558 %K RCC5559 %K RCC5560 %K RCC5561 %K RCC5562 %K RCC5563 %K RCC5564 %K RCC5565 %K RCC5566 %K RCC5567 %K RCC5568 %K RCC5569 %K RCC5570 %K RCC5571 %K RCC5572 %K RCC5573 %K RCC5574 %K RCC5575 %K RCC5576 %K RCC5577 %K RCC5578 %K RCC5579 %K RCC5580 %K RCC5581 %K RCC5582 %K RCC5583 %K RCC5584 %K RCC5585 %K RCC5586 %K RCC5587 %K RCC5588 %K RCC5589 %K RCC5590 %K RCC5591 %K RCC5592 %K RCC5593 %K RCC5594 %K RCC5595 %K RCC5596 %K RCC5597 %K RCC5598 %K RCC5599 %K RCC5600 %K RCC5601 %K RCC5602 %K RCC5603 %K RCC5604 %K RCC5605 %K RCC5606 %K RCC5607 %K RCC5608 %K RCC5609 %K RCC5610 %K RCC5611 %K RCC5612 %X Massive phytoplankton blooms develop at the Arctic ice edge, sometimes extending far under the pack ice. An extensive culturing effort was conducted before and during a phytoplankton bloom in Baffin Bay between April and July 2016. Different isolation strategies were applied, including flow cytometry cell sorting, manual single cell pipetting and serial dilution. Although all three techniques yielded the most common organisms, each technique retrieved specific taxa, highlighting the importance of using several methods to maximize the number and diversity of isolated strains. More than 1,000 cultures were obtained, characterized by 18S rRNA sequencing and optical microscopy and de-replicated to a subset of 276 strains presented in this work. Strains grouped into 57 genotypes defined by 100% 18S rRNA sequence similarity. These genotypes spread across five divisions: Heterokontophyta, Chlorophyta, Cryptophyta, Haptophyta and Dinophyta. Diatoms were the most abundant group (193 strains), mostly represented by the genera Chaetoceros and Attheya. The genera Rhodomonas and Pyramimonas were the most abundant non-diatom nanoplankton strains, while Micromonas polaris dominated the picoplankton. Diversity at the class level was higher during the peak of the bloom. Potentially new species were isolated, in particular within the genera Navicula, Nitzschia, Coscinodiscus, Thalassiosira, Pyramimonas, Mantoniella and Isochrysis. %B Elementa: Science of the Anthropocene %V 8 %P 6 %8 feb %G eng %U https://www.biorxiv.org/content/10.1101/642264v1 https://www.elementascience.org/article/10.1525/elementa.401/ %R 10.1525/elementa.401 %0 Journal Article %J Frontiers in Microbiology %D 2020 %T Dinoflagellate host chloroplasts and mitochondria remain functional during amoebophrya infection %A Kayal, Ehsan %A Alves-de-Souza, Catharina %A Farhat, Sarah %A Velo-Suarez, Lourdes %A Monjol, Joanne %A Szymczak, Jeremy %A Bigeard, Estelle %A Marie, Dominique %A Noel, Benjamin %A Porcel, Betina M %A Corre, Erwan %A Six, Christophe %A Guillou, Laure %K amoebophrya %K chloroplast %K Dinoflagellate %K frontiers in microbiology %K frontiersin %K kleptoplast %K marine plankton %K org %K organelles %K parasitism %K RCC1627 %K RCC4398 %K www %X Dinoflagellates are major components of phytoplankton that play critical roles in many microbial food webs, many of them being hosts of countless intracellular parasites. The phototrophic dinoflagellate Scrippsiella acuminata (Dinophyceae) can be infected by the microeukaryotic parasitoids Amoebophrya spp. (Syndiniales), some of which primarily target and digest the host nucleus. Early digestion of the nucleus at the beginning of the infection is expected to greatly impact the host metabolism, inducing the knockout of the organellar machineries that highly depend upon nuclear gene expression, such as the mitochondrial OXPHOS pathway and the plastid photosynthetic carbon fixation. However, previous studies have reported that chloroplasts remain functional in swimming host cells infected by Amoebophrya . We report here a multi-approach monitoring study of S. acuminata organelles over a complete infection cycle by nucleus-targeting Amoebophrya sp. strain A120. Our results show sustained and efficient photosystem II activity as a hallmark of functional chloroplast throughout the infection period despite the complete digestion of the host nucleus. We also report the importance played by light on parasite production, i.e., the amount of host biomass converted to parasite infective propagules. Using a differential gene expression analysis, we observed an apparent increase of all 3 mitochondrial and 9 out of the 11 plastidial genes involved in the electron transport chains (ETC) of the respiration pathways during the first stages of the infection. The longer resilience of organellar genes compared to those encoded by the nucleus suggests that both mitochondria and chloroplasts remain functional throughout most of the infection. This extended organelle functionality, along with higher parasite production under light conditions, suggests that host bioenergetic organelles likely benefit the parasite Amoebophrya sp. A120 and improve its fitness during the intracellular infective stage. %B Frontiers in Microbiology %V 11 %P 1–11 %8 dec %G eng %U https://www.frontiersin.org/articles/10.3389/fmicb.2020.600823/full %R 10.3389/fmicb.2020.600823 %0 Journal Article %J Genes %D 2020 %T Genome resolved biogeography of mamiellales %A Leconte %A Benites %A Vannier %A Wincker %A Piganeau %A Jaillon %K Biogeography %K mamiellales %K mating-type %K RCC1105 %K RCC2590 %K RCC299 %K RCC4221 %K RCC809 %K sexual reproduction %K tara oceans %X Among marine phytoplankton, Mamiellales encompass several species from the genera Micromonas, Ostreococcus and Bathycoccus, which are important contributors to primary production. Previous studies based on single gene markers described their wide geographical distribution but led to discussion because of the uneven taxonomic resolution of the method. Here, we leverage genome sequences for six Mamiellales species, two from each genus Micromonas, Ostreococcus and Bathycoccus, to investigate their distribution across 133 stations sampled during the Tara Oceans expedition. Our study confirms the cosmopolitan distribution of Mamiellales and further suggests non-random distribution of species, with two triplets of co-occurring genomes associated with different temperatures: Ostreococcus lucimarinus, Bathycoccus prasinos and Micromonas pusilla were found in colder waters, whereas Ostreococcus spp. RCC809, Bathycoccus spp. TOSAG39-1 and Micromonas commoda were more abundant in warmer conditions. We also report the distribution of the two candidate mating-types of Ostreococcus for which the frequency of sexual reproduction was previously assumed to be very low. Indeed, both mating types were systematically detected together in agreement with either frequent sexual reproduction or the high prevalence of a diploid stage. Altogether, these analyses provide novel insights into Mamiellales' biogeography and raise novel testable hypotheses about their life cycle and ecology. %B Genes %V 11 %P 66 %8 jan %G eng %U https://www.mdpi.com/2073-4425/11/1/66 %R 10.3390/genes11010066 %0 Journal Article %J Metabolomics %D 2020 %T Identification to species level of live single microalgal cells from plankton samples with matrix-free laser/desorption ionization mass spectrometry %A Baumeister, Tim U H %A Vallet, Marine %A Kaftan, Filip %A Guillou, Laure %A Svatoš, Aleš %A Pohnert, Georg %K ionization high- %K Live single-cell mass spectrometry %K matrix-free laser desorption %K Matrix-free laser desorption/ionization high-resol %K Metabolic fingerprinting %K Microalgal identification %K RCC1717 %K RCC2561 %K RCC2562 %K RCC3008 %K RCC4667 %K RCC5791 %K RCC6807 %K RCC6808 %K RCC6809 %K RCC6810 %K RCC6811 %K RCC6812 %K RCC6813 %K RCC6814 %K RCC6815 %K RCC6816 %K RCC6817 %K RCC6818 %K RCC6819 %K RCC6820 %K RCC6821 %K resolution mass spectrometry %K Spectral pattern matching %K Spectrum similarity %B Metabolomics %V 16 %P 28 %8 mar %G eng %U https://doi.org/10.1007/s11306-020-1646-7 http://link.springer.com/10.1007/s11306-020-1646-7 %R 10.1007/s11306-020-1646-7 %0 Journal Article %J Biomolecules %D 2020 %T Isoprostanoid profiling of marine microalgae %A Vigor, Claire %A Oger, Camille %A Reversat, Guillaume %A Rocher, Amandine %A Zhou, Bingqing %A Linares-Maurizi, Amandyne %A Guy, Alexandre %A Bultel-Poncé, Valérie %A Galano, Jean-Marie %A Vercauteren, Joseph %A Durand, Thierry %A Potin, Philippe %A Tonon, Thierry %A Leblanc, Catherine %K Isoprostanoids %K Micro-LC-MS/MS %K Microalgae %K Oxidative stress %K PUFAs %K RCC1349 %K RCC20 %K RCC69 %X ¡p¿Algae result from a complex evolutionary history that shapes their metabolic network. For example, these organisms can synthesize different polyunsaturated fatty acids, such as those found in land plants and oily fish. Due to the presence of numerous double-bonds, such molecules can be oxidized nonenzymatically, and this results in the biosynthesis of high-value bioactive metabolites named isoprostanoids. So far, there have been only a few studies reporting isoprostanoid productions in algae. To fill this gap, the current investigation aimed at profiling isoprostanoids by liquid chromatography -mass spectrometry/mass spectrometry (LC-MS/MS) in four marine microalgae. A good correlation was observed between the most abundant polyunsaturated fatty acids (PUFAs) produced by the investigated microalgal species and their isoprostanoid profiles. No significant variations in the content of oxidized derivatives were observed for Rhodomonas salina and Chaetoceros gracilis under copper stress, whereas increases in the production of C18-, C20- and C22-derived isoprostanoids were monitored in Tisochrysis lutea and Phaeodactylum tricornutum. In the presence of hydrogen peroxide, no significant changes were observed for C. gracilis and for T. lutea, while variations were monitored for the other two algae. This study paves the way to further studying the physiological roles of isoprostanoids in marine microalgae and exploring these organisms as bioresources for isoprostanoid production.¡/p¿ %B Biomolecules %V 10 %P 1073 %8 jul %G eng %U https://www.mdpi.com/2218-273X/10/7/1073 %R 10.3390/biom10071073 %0 Journal Article %J Algal Research %D 2020 %T Parallelisable non-invasive biomass, fitness and growth measurement of macroalgae and other protists with nephelometry %A Calmes, Benoît %A Strittmatter, Martina %A Jacquemin, Bertrand %A Perrineau, Marie Mathilde %A Rousseau, Céline %A Badis, Yacine %A Cock, J. Mark %A Destombe, Christophe %A Valero, Myriam %A Gachon, Claire M.M. %K Algal cultivation %K Biomass %K Biotechnology %K Nephelometry %K Phenotyping %K RCC149 %K RCC3088 %K RCC3510 %K rcc3553 %X With the exponential development of algal aquaculture and blue biotechnology, there is a strong demand for simple, inexpensive, high-throughput, quantitative phenotyping assays to measure the biomass, growth and fertility of algae and other marine protists. Here, we validate nephelometry, a method that relies on measuring the scattering of light by particles in suspension, as a non-invasive tool to measure in real-time the biomass of aquatic micro-organisms, such as microalgae, filamentous algae, as well as non-photosynthetic protists. Nephelometry is equally applicable to optic density and chlorophyll fluorescence measurements for the quantification of some microalgae, but outperforms other spectroscopy methods to quantify the biomass of biofilm-forming and filamentous algae, highly pigmented species and non-photosynthetic eukaryotes. Thanks to its insensitivity to the sample's pigmentation, nephelometry is also the method of choice when chlorophyll content varies between samples or time points, for example due to abiotic stress or pathogen infection. As examples, we illustrate how nephelometry can be combined with fluorometry or image analysis to monitor the quantity and time-course of spore release in fertile kelps or the progression of symptoms in diseased algal cultures. %B Algal Research %V 46 %P 101762 %G eng %U https://doi.org/10.1016/j.algal.2019.101762 %R 10.1016/j.algal.2019.101762 %0 Journal Article %J Phycologia %D 2020 %T Taxonomic reassignment of \textit{Pseudohaptolina birgeri comb. nov . (Haptophyta) %A Gérikas Ribeiro, Catherine %A Lopes dos Santos, Adriana %A Probert, Ian %A Vaulot, Daniel %A Edvardsen, Bente %K RCC5268 %K RCC5270 %B Phycologia %V in press %P 1–10 %8 oct %G eng %U https://www.biorxiv.org/content/10.1101/2020.05.06.081489v1 https://www.tandfonline.com/doi/full/10.1080/00318884.2020.1830255 %R 10.1080/00318884.2020.1830255 %0 Journal Article %J Science Advances %D 2020 %T Virus-host coexistence in phytoplankton through the genomic lens %A Yau, Sheree %A Krasovec, Marc %A Benites, L. Felipe %A Rombauts, Stephane %A Groussin, Mathieu %A Vancaester, Emmelien %A Aury, Jean-Marc %A Derelle, Evelyne %A Desdevises, Yves %A Escande, Marie-Line %A Grimsley, Nigel %A Guy, Julie %A Moreau, Hervé %A Sanchez-Brosseau, Sophie %A Van de Peer, Yves %A Vandepoele, Klaas %A Gourbière, Sébastien %A Piganeau, Gwenael %K RCC2590 %K RCC2596 %X Virus-microbe interactions in the ocean are commonly described by “boom and bust” dynamics, whereby a numerically dominant microorganism is lysed and replaced by a virus-resistant one. Here, we isolated a microalga strain and its infective dsDNA virus whose dynamics are characterized instead by parallel growth of both the microalga and the virus. Experimental evolution of clonal lines revealed that this viral production originates from the lysis of a minority of virus-susceptible cells, which are regenerated from resistant cells. Whole-genome sequencing demonstrated that this resistant-susceptible switch involved a large deletion on one chromosome. Mathematical modeling explained how the switch maintains stable microalga-virus population dynamics consistent with their observed growth pattern. Comparative genomics confirmed an ancient origin of this “accordion” chromosome despite a lack of sequence conservation. Together, our results show how dynamic genomic rearrangements may account for a previously overlooked coexistence mechanism in microalgae-virus interactions. %B Science Advances %V 6 %P eaay2587 %8 apr %G eng %U https://advances.sciencemag.org/lookup/doi/10.1126/sciadv.aay2587 %R 10.1126/sciadv.aay2587 %0 Journal Article %J Frontiers in Microbiology %D 2020 %T Visualization of viral infection dynamics in a unicellular eukaryote and quantification of viral production using virus fluorescence in situ hybridization %A Castillo, Yaiza M. %A Sebastián, Marta %A Forn, Irene %A Grimsley, Nigel %A Yau, Sheree %A Moraru, Cristina %A Vaqué, Dolors %K culture system %K marine picoeukaryote %K Ostreococcus tauri %K Ostreococcus tauri virus 5 %K RCC4221 %K virus fluorescence in situ hybridization %K virus-host interactions %X One of the major challenges in viral ecology is to assess the impact of viruses in controlling the abundance of specific hosts in the environment. To this end, techniques that enable the detection and quantification of virus-host interactions at the single-cell level are essential. With this goal in mind, we implemented virus fluorescence in situ hybridization (VirusFISH) using as a model the marine picoeukaryote Ostreococcus tauri and its virus Ostreococcus tauri virus 5 (OtV5). VirusFISH allowed the visualization and quantification of the proportion of infected cells during an infection cycle in experimental conditions. We were also able to quantify the abundance of free viruses released during cell lysis, discriminating OtV5 from other mid-level fluorescence phages in our non-axenic infected culture that were not easily distinguishable with flow cytometry. Our results showed that although the major lysis of the culture occurred between 24 and 48 h after OtV5 inoculation, some new viruses were already produced between 8 and 24 h. With this work, we demonstrate that VirusFISH is a promising technique to study specific virus-host interactions in non-axenic cultures and establish a framework for its application in complex natural communities. %B Frontiers in Microbiology %V 11 %P 1559 %8 jul %G eng %U https://www.frontiersin.org/article/10.3389/fmicb.2020.01559/full %R 10.3389/fmicb.2020.01559 %0 Journal Article %J Current Biology %D 2019 %T Algal remodeling in a ubiquitous planktonic photosymbiosis %A Decelle, Johan %A Stryhanyuk, Hryhoriy %A Gallet, Benoit %A Veronesi, Giulia %A Schmidt, Matthias %A Balzano, Sergio %A Marro, Sophie %A Uwizeye, Clarisse %A Jouneau, Pierre-Henri %A Lupette, Josselin %A Jouhet, Juliette %A Maréchal, Éric %A Schwab, Yannick %A Schieber, Nicole L. %A Tucoulou, Rémi %A Richnow, Hans %A Finazzi, Giovanni %A Musat, Niculina %K RCC1719 %X Photosymbiosis between single-celled hosts and microalgae is common in oceanic plankton, especially in oligotrophic surface waters. However, the functioning of this ecologically important cell-cell interaction and the subcellular mechanisms allowing the host to accommodate and benefit from its microalgae remain enigmatic. Here, using a combination of quantitative single-cell structural and chemical imaging techniques (FIB-SEM, nanoSIMS, Synchrotron X-ray fluorescence), we show that the structural organization, physiology, and trophic status of the algal symbionts (the haptophyte Phaeocystis) significantly change within their acantharian hosts compared to their free-living phase in culture. In symbiosis, algal cell division is blocked, photosynthesis is enhanced, and cell volume is increased by up to 10-fold with a higher number of plastids (from 2 to up to 30) and thylakoid membranes. The multiplication of plastids can lead to a 38-fold increase of the total plastid volume in a cell. Subcellular mapping of nutrients (nitrogen and phosphorous) and their stoichiometric ratios shows that symbiotic algae are impoverished in phosphorous and suggests a higher investment in energy-acquisition machinery rather than in growth. Nanoscale imaging also showed that the host supplies a substantial amount of trace metals (e.g., iron and cobalt), which are stored in algal vacuoles at high concentrations (up to 660 ppm). Sulfur mapping reveals a high concentration in algal vacuoles that may be a source of antioxidant molecules. Overall, this study unveils an unprecedented morphological and metabolic transformation of microalgae following their integration into a host, and it suggests that this widespread symbiosis is a farming strategy wherein the host engulfs and exploits microalgae. %B Current Biology %V 29 %P 968–978.e4 %8 mar %G eng %U https://www.sciencedirect.com/science/article/abs/pii/S0960982219301320#undfig1 %R 10.1016/J.CUB.2019.01.073 %0 Journal Article %J Current Biology %D 2019 %T Alternative mechanisms for fast na + /ca 2+ signaling in eukaryotes via a novel class of single-domain voltage-gated channels %A Helliwell, Katherine E. %A Chrachri, Abdul %A Koester, Julie A. %A Wharam, Susan %A Verret, Frederic %A Taylor, Alison R. %A Wheeler, Glen L. %A Brownlee, Colin %K action potentials %K BacNa v %K calcium channel %K diatoms %K EukCats %K gliding motility %K ion selectivity %K RCC299 %K signaling %K single-domain channel %K voltage-gated channel %X Rapid Na + /Ca 2+ -based action potentials govern essential cellular functions in eukaryotes, from the motile responses of unicellular protists, such as Paramecium [1, 2], to complex animal neuromuscular activity [3]. A key innovation underpinning this fundamental signaling process has been the evolution of four-domain voltage-gated Na + /Ca 2+ channels (4D-Ca v s/Na v s). These channels are widely distributed across eukaryote diversity [4], albeit several eukaryotes, including land plants and fungi, have lost voltage-sensitive 4D-Ca v /Na v s [5–7]. Because these lineages appear to lack rapid Na + /Ca 2+ -based action potentials, 4D-Ca v /Na v s are generally considered necessary for fast Na + /Ca 2+ -based signaling [7]. However, the cellular mechanisms underpinning the membrane physiology of many eukaryotes remain unexamined. Eukaryotic phytoplankton critically influence our climate as major primary producers. Several taxa, including the globally abundant diatoms, exhibit membrane excitability [8–10]. We previously demonstrated that certain diatom genomes encode 4D-Ca v /Na v s [4] but also proteins of unknown function, resembling prokaryote single-domain, voltage-gated Na + channels (BacNa v s) [4]. Here, we show that single-domain channels are actually broadly distributed across major eukaryote phytoplankton lineages and represent three novel classes of single-domain channels, which we refer collectively to as EukCats. Functional characterization of diatom EukCatAs indicates that they are voltage-gated Na + - and Ca 2+ -permeable channels, with rapid kinetics resembling metazoan 4D-Ca v s/Na v s. In Phaeodactylum tricornutum, which lacks 4D-Ca v /Na v s, EukCatAs underpin voltage-activated Ca 2+ signaling important for membrane excitability, and mutants exhibit impaired motility. EukCatAs therefore provide alternative mechanisms for rapid Na + /Ca 2+ signaling in eukaryotes and may functionally replace 4D-Ca v s/Na v s in pennate diatoms. Marine phytoplankton thus possess unique signaling mechanisms that may be key to environmental sensing in the oceans. Diatoms exhibit fast animal-like action potentials, but many species lack 4D-Ca v /Na v channels that underpin membrane excitability in animals. Diatoms do encode novel 1D voltage-gated channels (EukCatAs). Helliwell, Chrachri et al. show that EukCatAs are fast Na + and Ca 2+ channels that provide alternative mechanisms for rapid signaling in eukaryotes. %B Current Biology %V 29 %P 1503–1511.e6 %G eng %R 10.1016/j.cub.2019.03.041 %0 Thesis %D 2019 %T Computational and experimental models of diatom-bacteria interaction %A van Tol, Helena M %K Croceibacter atlanticus %K diatoms %K Genome-scale met %K RCC80 %X Microbial interactions structure ecosystems and fuel biogeochemical cycling. The metabolic activities operating in the ocean are critical to the entire planet. In this work, I focused on interactions between diatoms and heterotrophic bacteria. Diatoms are a group of unicellular brown algae with frustules composed of silica. They form the base of coastal and polar marine food webs and contribute one fifth of global primary productivity. The inorganic nutrients fixed by oxygenic photosynthesis fuel secondary productivity by marine bacteria. Marine bacteria and diatoms have a range of different interaction strategies; many are still being elucidated.In Chapter 1, I studied the antagonistic effects of a flavobacterium on diatom cell division. Croceibacter atlanticus inhibits cytokinesis in many species, causing the cells to elongate, become mutlinucleated, and filled with plastids.In Chapter 2, I created a metabolic model of the diatom Thalassiosira pseudonana using the genome and physiological data from the literature. Simulations of diatom growth using Flux Balance Analysis revealed a role for nitrate and sulfate assimilation in dissipating reductants from the plastid. Changing redox and nutrient conditions causes the cell to secrete metabolites including organic carbon, nitrogen, and sulfur.In Chapter 3, I created a metabolic model of the B12-producing alphaproteobacterium Ruegeria pomeroyi. Previous work has demonstrated that R. pomeroyi will provide cobalamin to T. pseudonana in B12-starvation conditions in exchange for organic sulfur and nitrogen. I constrained the metabolic models with transcriptomic data of T. pseudonana and R. pomeroyi in co-culture and simulated their interaction.The distinct character of metabolites produced by diatoms likely fuels interactions with bacteria capable of utilizing those molecules. Bacteria influence diatom metabolism by interfering with the cell cycle, through nutrient-limitation, by altering redox conditions, and providing the cofactors required for growth. In this work, I have contributed to the literature exploring the complexity of diatom-bacteria interactions, where chemical or peptide cues, signals, and antagonists underlie the dynamics of microbial interactions. I have also created a framework for exploring more general metabolic exchanges between diatoms and bacteria. Genome-scale metabolic modeling of interactions between distinct marine microbial communities may be key to accurately predicting the character of dissolve organic matter in the ocean. %G eng %U https://remotexs.ntu.edu.sg/user/login?url=https://search.proquest.com/docview/2305846221?accountid=12665 %9 phd %0 Journal Article %J Journal of Phycology %D 2019 %T Effects of elevated co 2 on growth, calcification and spectral dependence of photoinhibition in the coccolithophore Emiliania huxleyi (Prymnesiophyceae) %A Lorenzo, M. Rosario %A Neale, Patrick J. %A Sobrino, Cristina %A León, Pablo %A Vázquez, Víctor %A Bresnan, Eileen %A Segovia, María %K rcc1226 %B Journal of Phycology %P jpy.12885 %8 may %G eng %U https://onlinelibrary.wiley.com/doi/abs/10.1111/jpy.12885 %R 10.1111/jpy.12885 %0 Journal Article %J Organic Geochemistry %D 2019 %T Hydrogen isotope fractionation response to salinity and alkalinity in a calcifying strain of Emiliania huxleyi %A Weiss, Gabriella M. %A Roepert, Anne %A Middelburg, Jack J. %A Schouten, Stefan %A Sinninghe Damsté, Jaap S. %A van der Meer, Marcel T.J. %K RCC2050 %B Organic Geochemistry %8 jun %G eng %U https://linkinghub.elsevier.com/retrieve/pii/S0146638019301020 %R 10.1016/j.orggeochem.2019.06.001 %0 Journal Article %J Phytochemistry %D 2019 %T NMR characterization and evaluation of antibacterial and antiobiofilm activity of organic extracts from stationary phase batch cultures of five marine microalgae (Dunaliella sp., D. salina, Chaetoceros calcitrans, C. gracilis and Tisochrysis lutea) %A Iglesias, Ma José %A Soengas, Raquel %A Probert, Ian %A Guilloud, Emilie %A Gourvil, Priscillia %A Mehiri, Mohamed %A López, Yuly %A Cepas, Virginio %A Gutiérrez-del-Río, Ignacio %A Redondo-Blanco, Saúl %A Villar, Claudio J. %A Lombó, Felipe %A Soto, Sara %A Ortiz, Fernando López %K Antibacterial %K Antibiofilm %K Chaetoceros %K Dunaliella %K Metabolite identification %K NMR %K RCC1349 %K RCC1811 %K RCC3579 %K RCC5 %K RCC5953 %K Tisochrysis %B Phytochemistry %V 164 %P 192–205 %8 aug %G eng %U https://linkinghub.elsevier.com/retrieve/pii/S0031942219300184 %R 10.1016/j.phytochem.2019.05.001 %0 Journal Article %J Molecules %D 2019 %T What is in store for EPS microalgae in the next decade? %A Pierre, Guillaume %A Delattre, Cédric %A Dubessay, Pascal %A Jubeau, Sébastien %A Vialleix, Carole %A Cadoret, Jean-Paul %A Probert, Ian %A Michaud, Philippe %K application %K eps %K exopolysaccharides %K market %K Microalgae %X Microalgae and their metabolites have been an El Dorado since the turn of the 21st century. Many scientific works and industrial exploitations have thus been set up. These developments have often highlighted the need to intensify the processes for biomass production in photo-autotrophy and exploit all the microalgae value including ExoPolySaccharides (EPS). Indeed, the bottlenecks limiting the development of low value products from microalgae are not only linked to biology but also to biological engineering problems including harvesting, recycling of culture media, photoproduction, and biorefinery. Even respecting the so-called “Biorefinery Concept”, few applications had a chance to emerge and survive on the market. Thus, exploiting EPS from microalgae for industrial applications in some low-value markets such as food is probably not a mature proposition considering the competitiveness of polysaccharides from terrestrial plants, macroalgae, and bacteria. However, it does not imply drawing a line on their uses but rather “thinking them” differently. This review provides insights into microalgae, EPS, and their exploitation. Perspectives on issues affecting the future of EPS microalgae are also addressed with a critical point of view. %B Molecules %V 24 %P 4296 %8 nov %G eng %U https://www.mdpi.com/1420-3049/24/23/4296 %R 10.3390/molecules24234296 %0 Journal Article %J Frontiers in Marine Science %D 2018 %T Bolidophyceae, a sister picoplanktonic group of diatoms – a review %A Kuwata, Akira %A Yamada, Kazumasa %A Ichinomiya, Mutsuo %A Yoshikawa, Shinya %A Tragin, Margot %A Vaulot, Daniel %A Lopes dos Santos, Adriana %K RCC1657 %K RCC201 %K RCC205 %K RCC206 %K rcc212 %K RCC239 %B Frontiers in Marine Science %V 5 %P 370 %8 oct %G eng %U https://www.frontiersin.org/article/10.3389/fmars.2018.00370/full %R 10.3389/fmars.2018.00370 %0 Journal Article %J Science Advances %D 2018 %T Endocytosis-mediated siderophore uptake as a strategy for Fe acquisition in diatoms %A Kazamia, Elena %A Sutak, Robert %A Paz-Yepes, Javier %A Dorrell, Richard G %A Vieira, Fabio Rocha Jimenez %A Mach, Jan %A Morrissey, Joe %A Leon, Sébastien %A Lam, France %A Pelletier, Eric %A Camadro, Jean-michel %A Bowler, Chris %A Lesuisse, Emmanuel %K RCC2967 %B Science Advances %V 4 %P eaar4536 %8 may %G eng %U http://advances.sciencemag.org/lookup/doi/10.1126/sciadv.aar4536 %R 10.1126/sciadv.aar4536 %0 Journal Article %J iScience %D 2018 %T Infection dynamics of a bloom-forming alga and its virus determine airborne coccolith emission from seawater %A Trainic, Miri %A Koren, Ilan %A Sharoni, Shlomit %A Frada, Miguel %A Segev, Lior %A Rudich, Yinon %A Vardi, Assaf %K Atmospheric Science %K Biogeoscience %K Earth Sciences %K Marine Organism %K RCC1216 %X Summary Sea spray aerosols (SSA), have a profound effect on the climate; however, the contribution of oceanic microbial activity to SSA is not fully established. We assessed aerosolization of the calcite units (coccoliths) that compose the exoskeleton of the cosmopolitan bloom-forming coccolithophore, Emiliania huxleyi. Airborne coccolith emission occurs in steady-state conditions and increases by an order of magnitude during E. huxleyi infection by E. huxleyi virus (EhV). Airborne to seawater coccolith ratio is 1:108, providing estimation of airborne concentrations from seawater concentrations. The coccoliths' unique aerodynamic structure yields a characteristic settling velocity of \~0.01 cm s-1, \~25 times slower than average sea salt particles, resulting in coccolith fraction enrichment in the air. The calculated enrichment was established experimentally, indicating that coccoliths may be key contributors to coarse mode SSA surface area, comparable with sea salt aerosols. This study suggests a coupling between key oceanic microbial interactions and fundamental atmospheric processes like SSA formation. %B iScience %8 aug %G eng %U https://www.cell.com/iscience/fulltext/S2589-0042(18)30105-6 https://linkinghub.elsevier.com/retrieve/pii/S2589004218301056 %R 10.1016/j.isci.2018.07.017 %0 Journal Article %J Scientific Reports %D 2018 %T Integrative analysis of large scale transcriptome data draws a comprehensive landscape of Phaeodactylum tricornutum genome and evolutionary origin of diatoms %A Rastogi, Achal %A Maheswari, Uma %A Dorrell, Richard G. %A Vieira, Fabio Rocha Jimenez %A Maumus, Florian %A Kustka, Adam %A McCarthy, James %A Allen, Andy E. %A Kersey, Paul %A Bowler, Chris %A Tirichine, Leila %K RCC2967 %X 2 3 Diatoms are one of the most successful and ecologically important groups of eukaryotic 4 phytoplankton in the modern ocean. Deciphering their genomes is a key step towards better 5 understanding of their biological innovations, evolutionary origins, and ecological 6 underpinnings. Here, we have used 90 RNA-Seq datasets from different growth conditions 7 combined with published expressed sequence tags and protein sequences from multiple taxa 8 to explore the genome of the model diatom Phaeodactylum tricornutum, and introduce 1,489 9 novel genes. The new annotation additionally permitted the discovery for the first time of 10 extensive alternative splicing (AS) in diatoms, including intron retention and exon skipping 11 which increases the diversity of transcripts to regulate gene expression in response to nutrient 12 limitations. In addition, we have used up-to-date reference sequence libraries to dissect the 13 taxonomic origins of diatom genomes. We show that the P. tricornutum genome is replete in 14 lineage-specific genes, with up to 47% of the gene models present only possessing 15 orthologues in other stramenopile groups. Finally, we have performed a comprehensive de 16 novo annotation of repetitive elements showing novel classes of TEs such as SINE, MITE, LINE 17 and TRIM/LARD. This work provides a solid foundation for future studies of diatom gene 18 function, evolution and ecology. %B Scientific Reports %V 8 %P 4834 %8 dec %G eng %U https://www.biorxiv.org/content/early/2017/08/14/176024%0Ahttp://dx.doi.org/10.1101/176024 http://www.nature.com/articles/s41598-018-23106-x %R 10.1038/s41598-018-23106-x %0 Journal Article %J Scientific Reports %D 2018 %T A novel species of the marine cyanobacterium Acaryochloris with a unique pigment content and lifestyle %A Partensky, Frédéric %A Six, Christophe %A Ratin, Morgane %A Garczarek, Laurence %A Vaulot, Daniel %A Probert, Ian %A Calteau, Alexandra %A Gourvil, Priscillia %A Marie, Dominique %A Grébert, Théophile %A Bouchier, Christiane %A Le Panse, Sophie %A Gachenot, Martin %A Rodríguez, Francisco %A Garrido, José L. %K RCC1774 %B Scientific Reports %V 8 %P 9142 %8 dec %G eng %U http://www.nature.com/articles/s41598-018-27542-7 %R 10.1038/s41598-018-27542-7 %0 Journal Article %J Geobiology %D 2018 %T Stable isotope fractionation of strontium in coccolithophore calcite: Influence of temperature and carbonate chemistry %A Müller, M N %A Krabbenhöft, A %A Vollstaedt, H %A Brandini, F P %A Eisenhauer, A %K coccolithophores %K paleoproxy calibration %K phytoplankton %K RCC1200 %K stable Sr isotope fractionation %X Abstract Marine calcifying eukaryotic phytoplankton (coccolithophores) is a major contributor to the pelagic production of CaCO3 and plays an important role in the biogeochemical cycles of C, Ca and other divalent cations present in the crystal structure of calcite. The geochemical signature of coccolithophore calcite is used as palaeoproxy to reconstruct past environmental conditions and to understand the underlying physiological mechanisms (vital effects) and precipitation kinetics. Here, we present the stable Sr isotope fractionation between seawater and calcite (?88/86Sr) of laboratory cultured coccolithophores in individual dependence of temperature and seawater carbonate chemistry. Coccolithophores were cultured within a temperature and a pCO2 range from 10 to 25°C and from 175 to 1,240 ?atm, respectively. Both environmental drivers induced a significant linear increase in coccolith stable Sr isotope fractionation. The temperature correlation at constant pCO2 for Emiliania huxleyi and Coccolithus braarudii is expressed as ?88/86Sr = ?7.611 ? 10?3 T + 0.0061. The relation of ?88/86Sr to pCO2 was tested in Emiliania huxleyi at 10 and 20°C and resulted in ?88/86Sr = ?5.394 ? 10?5 pCO2 ? 0.0920 and ?88/86Sr = ?5.742 ? 10?5 pCO2 ? 0.1351, respectively. No consistent relationship was found between coccolith ?88/86Sr and cellular physiology impeding a direct application of fossil coccolith ?88/86Sr as coccolithophore productivity proxy. An overall significant correlation was detected between the elemental distribution coefficient (DSr) and ?88/86Sr similar to inorganic calcite with a physiologically induced offset. Our observations indicate (i) that temperature and pCO2 induce specific effects on coccolith ?88/86Sr values and (ii) that strontium elemental ratios and stable isotope fractionation are mainly controlled by precipitation kinetics when embedded into the crystal lattice and subject to vital effects during the transmembrane transport from seawater to the site of calcification. These results provide an important step to develop a coccolith ?88/86Sr palaeoproxy complementing the existing toolbox of palaeoceanography. %B Geobiology %V 16 %P 297–306 %8 may %G eng %U https://doi.org/10.1111/gbi.12276 %R 10.1111/gbi.12276 %0 Journal Article %J Scientific Reports %D 2017 %T Chloropicophyceae, a new class of picophytoplanktonic prasinophytes %A Lopes dos Santos, Adriana %A Pollina, Thibaut %A Gourvil, Priscillia %A Corre, Erwan %A Marie, Dominique %A Garrido, José Luis %A Rodríguez, Francisco %A Noël, Mary-Hélène %A Vaulot, Daniel %A Eikrem, Wenche %K 2017 %K RCC1019 %K RCC1021 %K RCC1032 %K RCC1043 %K RCC1124 %K RCC138 %K RCC15 %K RCC1871 %K RCC19 %K RCC227 %K RCC2335 %K RCC2337 %K RCC2339 %K RCC287 %K RCC297 %K RCC3368 %K RCC3373 %K RCC3374 %K RCC3375 %K RCC3376 %K RCC3402 %K RCC4429 %K RCC4430 %K RCC4434 %K RCC4572 %K RCC4656 %K RCC696 %K RCC700 %K RCC701 %K RCC712 %K RCC713 %K RCC717 %K RCC719 %K RCC722 %K RCC726 %K RCC856 %K RCC857 %K RCC887 %K RCC917 %K RCC996 %K RCC997 %K RCC998 %K RCC999 %K sbr?hyto$_\textrmd$ipo %B Scientific Reports %V 7 %P 14019 %8 dec %G eng %U http://www.nature.com/articles/s41598-017-12412-5 %R 10.1038/s41598-017-12412-5 %0 Journal Article %J The ISME Journal %D 2017 %T Diversity and oceanic distribution of prasinophytes clade VII, the dominant group of green algae in oceanic waters %A Lopes dos Santos, Adriana %A Gourvil, Priscillia %A Tragin, Margot %A Noël, Mary-Hélène %A Decelle, Johan %A Romac, Sarah %A Vaulot, Daniel %K 2016 %K MACUMBA %K MicroB3 %K RCC1019 %K RCC1021 %K RCC1032 %K RCC1043 %K RCC1124 %K RCC138 %K RCC15 %K RCC1871 %K RCC19 %K RCC227 %K RCC2335 %K RCC2337 %K RCC2339 %K RCC287 %K RCC297 %K RCC3368 %K RCC3373 %K RCC3374 %K RCC3375 %K RCC3376 %K RCC3402 %K RCC4429 %K RCC4430 %K RCC4434 %K RCC4656 %K RCC696 %K RCC700 %K RCC701 %K RCC712 %K RCC713 %K RCC717 %K RCC719 %K RCC722 %K RCC726 %K RCC856 %K RCC857 %K RCC917 %K RCC996 %K RCC997 %K RCC998 %K RCC999 %K sbr?hyto$_\textrmd$ipo %K sbr?hyto?ppo %B The ISME Journal %V 11 %P 512–528 %8 feb %G eng %U http://www.nature.com/doifinder/10.1038/ismej.2016.120 %R 10.1038/ismej.2016.120 %0 Journal Article %J Journal of Phycology %D 2017 %T Improvement of phytoplankton culture isolation using single cell sorting by flow cytometry %A Marie, Dominique %A Le Gall, Florence %A Edern, Roseline %A Gourvil, Priscillia %A Vaulot, Daniel %E Valentin, K. %K 2016 %K RCC1008 %K RCC299 %K RCC350 %K RCC4108 %K RCC4548 %K RCC4549 %K RCC4550 %K RCC4551 %K RCC4552 %K RCC4553 %K RCC4554 %K RCC4555 %K RCC4556 %K RCC4557 %K RCC4558 %K RCC4559 %K RCC4560 %K RCC4561 %K RCC4562 %K RCC4563 %K RCC4564 %K RCC4565 %K RCC4566 %K RCC4567 %K RCC4568 %K RCC4569 %K RCC4570 %K RCC4571 %K RCC4572 %K RCC4573 %K RCC4574 %K RCC4575 %K RCC4576 %K RCC4577 %K RCC4578 %K RCC4579 %K RCC4657 %K RCC4658 %K RCC4659 %K RCC4660 %K RCC4661 %K RCC4662 %K RCC4663 %K RCC4664 %K RCC4665 %K RCC4666 %K RCC90 %B Journal of Phycology %V 53 %P 271–282 %8 apr %G eng %U http://doi.wiley.com/10.1111/jpy.12495 %R 10.1111/jpy.12495 %0 Journal Article %J Journal of Phycology %D 2017 %T Morphological and genetic diversity of Beaufort Sea diatoms with high contributions from the Chaetoceros neogracilis species complex %A Balzano, Sergio %A Percopo, Isabella %A Siano, Raffaele %A Gourvil, Priscillia %A Chanoine, Mélanie %A Marie, Dominique %A Vaulot, Daniel %A Sarno, Diana %E Wood, M. %K RCC1984 %K RCC1985 %K RCC1986 %K RCC1988 %K RCC1989 %K RCC1990 %K RCC1991 %K RCC1992 %K RCC1993 %K RCC1995 %K RCC1997 %K RCC1999 %K RCC2000 %K RCC2002 %K RCC2003 %K RCC2004 %K RCC2005 %K RCC2006 %K RCC2008 %K RCC2010 %K RCC2011 %K RCC2012 %K RCC2014 %K RCC2016 %K RCC2017 %K RCC2021 %K RCC2037 %K RCC2038 %K RCC2039 %K RCC2042 %K RCC2043 %K RCC2261 %K RCC2262 %K RCC2263 %K RCC2264 %K RCC2265 %K RCC2266 %K RCC2267 %K RCC2268 %K RCC2269 %K RCC2270 %K RCC2272 %K RCC2273 %K RCC2274 %K RCC2275 %K RCC2276 %K RCC2277 %K RCC2278 %K RCC2279 %K RCC2280 %K RCC2281 %K RCC2282 %K RCC2318 %K RCC2506 %K RCC2517 %K RCC2520 %K RCC2521 %K RCC2522 %X Seventy-five diatom strains isolated from the Beaufort Sea (Canadian Arctic) in the summer of 2009 were characterized by light and electron microscopy (SEM and TEM), as well as 18S and 28S rRNA gene sequencing. These strains group into 20 genotypes and 17 morphotypes and are affiliated with the genera Arcocellulus, Attheya, Chaetoceros, Cylindrotheca, Eucampia, Nitzschia, Porosira, Pseudo-nitzschia, Shionodiscus, Thalassiosira, and Synedropsis. Most of the species have a distribution confined to the northern/polar area. Chaetoceros neogracilis and Chaetoceros gelidus were the most represented taxa. Strains of C. neogracilis were morphologically similar and shared identical 18S rRNA gene sequences, but belonged to four distinct genetic clades based on 28S rRNA, ITS-1 and ITS-2 phylogenies. Secondary structure prediction revealed that these four clades differ in hemi-compensatory base changes (HCBCs) in paired positions of the ITS-2, suggesting their inability to interbreed. Reproductively isolated C. neogracilis genotypes can thus co-occur in summer phytoplankton communities in the Beaufort Sea. C. neogracilis generally occurred as single cells but also formed short colonies. It is phylogenetically distinct from an Antarctic species, erroneously identified in some previous studies as C. neogracilis, but named here as Chaetoceros sp. This work provides taxonomically validated sequences for 20 Arctic diatom taxa, which will facilitate future metabarcoding studies on phytoplankton in this region. %B Journal of Phycology %V 53 %P 161–187 %8 feb %G eng %U http://doi.wiley.com/10.1111/jpy.12489 %R 10.1111/jpy.12489 %0 Journal Article %J PLOS ONE %D 2017 %T Responses of the picoprasinophyte Micromonas commoda to light and ultraviolet stress %A Cuvelier, Marie L %A Guo, Jian %A Ortiz, Alejandra C. %A van Baren, Marijke J. %A Tariq, Muhammad Akram %A Partensky, Frédéric %A Worden, Alexandra Z %E Cockshutt, Amanda M. %K RCC299 %B PLOS ONE %V 12 %P e0172135 %8 mar %G eng %U http://dx.plos.org/10.1371/journal.pone.0172135 %R 10.1371/journal.pone.0172135 %0 Journal Article %J Protist %D 2017 %T Revision of the genus micromonas manton et parke (chlorophyta, mamiellophyceae), of the type species m. pusilla (butcher) manton & parke and of the species m. commoda van baren, bachy and worden and description of two new species based on the genetic %A Simon, Nathalie %A Foulon, Elodie %A Grulois, Daphne %A Six, Christophe %A Desdevises, Yves %A Latimier, Marie %A Le Gall, Florence %A Tragin, Margot %A Houdan, Aude %A Derelle, Evelyne %A Jouenne, Fabien %A Marie, Dominique %A Le Panse, Sophie %A Vaulot, Daniel %A Marin, Birger %K 2017 %K ASSEMBLE %K rcc %K RCC1109 %K RCC114 %K RCC2306 %K RCC2308 %K RCC299 %K RCC372 %K RCC373 %K RCC418 %K RCC434 %K RCC447 %K RCC448 %K RCC449 %K RCC450 %K RCC451 %K RCC461 %K RCC465 %K RCC472 %K RCC497 %K RCC498 %K RCC570 %K RCC629 %K RCC647 %K RCC658 %K RCC676 %K RCC692 %K RCC746 %K RCC803 %K RCC804 %K RCC805 %K RCC806 %K RCC807 %K RCC808 %K RCC828 %K RCC829 %K RCC830 %K RCC831 %K RCC833 %K RCC834 %K RCC835 %K RCC836 %K SBR$_\textrmP$hyto$_\textrmD$IPO %K SBR$_\textrmP$hyto$_\textrmP$PM %K sbr?hyto$_\textrmd$ipo %B Protist %V 168 %P 612–635 %8 nov %G eng %U http://linkinghub.elsevier.com/retrieve/pii/S1434461017300780 %R 10.1016/j.protis.2017.09.002 %0 Journal Article %J The ISME Journal %D 2017 %T Ubiquitous marine bacterium inhibits diatom cell division %A van Tol, Helena M %A Amin, Shady A %A Armbrust, E Virginia %K 2016 %K RCC80 %B The ISME Journal %V 11 %P 31–42 %8 jan %G eng %U http://dx.doi.org/10.1038/ismej.2016.112 http://www.nature.com/doifinder/10.1038/ismej.2016.112 %R 10.1038/ismej.2016.112 %0 Journal Article %J The ISME Journal %D 2017 %T Use of plankton-derived vitamin B1 precursors, especially thiazole-related precursor, by key marine picoeukaryotic phytoplankton %A Paerl, Ryan W %A Bouget, François-Yves %A Lozano, Jean-Claude %A Vergé, Valérie %A Schatt, Philippe %A Allen, Eric E %A Palenik, Brian %A Azam, Farooq %K rcc3401 %K RCC745 %B The ISME Journal %V 11 %P 753–765 %8 mar %G eng %U http://www.nature.com/doifinder/10.1038/ismej.2016.145 %R 10.1038/ismej.2016.145 %0 Journal Article %J Perspectives in Phycology %D 2016 %T Diversity and distribution of haptophytes revealed by environmental sequencing and metabarcoding – a review %A Edvardsen, Bente %A Egge, Elianne Sirnaes %A Vaulot, Daniel %K 2016 %K rcc %K sbr?hyto$_\textrmd$ipo %B Perspectives in Phycology %V 3 %P 77–91 %8 apr %G eng %U https://dx.doi.org/10.6084/m9.figshare.2759983.v1 http://www.schweizerbart.de/papers/pip/detail/3/85671/Diversity_and_distribution_of_haptophytes_revealed?af=crossref %R 10.1127/pip/2016/0052 %0 Journal Article %J The ISME Journal %D 2016 %T Diversity and oceanic distribution of Parmales (Bolidophyceae), a picoplankton group closely related to diatoms %A Ichinomiya, Mutsuo %A Lopes dos Santos, A %A Gourvil, Priscillia %A Yoshikawa, Shinya %A Kamiya, Mitsunobu %A Ohki, Kaori %A Audic, S %A de Vargas, Colomban %A Vaulot, Daniel %A Kuwata, Akira %K 2016 %K MACUMBA %K MicroB3 %K rcc %K SBR$_\textrmP$hyto$_\textrmD$PO %K sbr?hyto$_\textrmd$ipo %K sbr?hyto?ppo %B The ISME Journal %V in press %G eng %R 10.1038/ismej.2016.38 %0 Journal Article %J PloS one %D 2016 %T Identifying aspects of the post-transcriptional program governing the proteome of the green alga micromonas pusilla. %A Waltman, Peter H %A Guo, Jian %A Reistetter, Emily Nahas %A Purvine, Samuel %A Ansong, Charles K %A van Baren, Marijke J %A Wong, Chee-Hong %A Wei, Chia-Lin %A Smith, Richard D %A Callister, Stephen J %A Stuart, Joshua M %A Worden, Alexandra Z %K 2016 %K rcc %K RCC834 %X Micromonas is a unicellular motile alga within the Prasinophyceae, a green algal group that is related to land plants. This picoeukaryote (¡2 ??m diameter) is widespread in the marine environment but is not well understood at the cellular level. Here, we examine shifts in mRNA and protein expression over the course of the day-night cycle using triplicated mid-exponential, nutrient replete cultures of Micromonas pusilla CCMP1545. Samples were collected at key transition points during the diel cycle for evaluation using high-throughput LC-MS proteomics. In conjunction, matched mRNA samples from the same time points were sequenced using pair-ended directional Illumina RNA-Seq to investigate the dynamics and relationship between the mRNA and protein expression programs of M. pusilla. Similar to a prior study of the marine cyanobacterium Prochlorococcus, we found significant divergence in the mRNA and proteomics expression dynamics in response to the light:dark cycle. Additionally, expressional responses of genes and the proteins they encoded could also be variable within the same metabolic pathway, such as we observed in the oxygenic photosynthesis pathway. A regression framework was used to predict protein levels from both mRNA expression and gene-specific sequence-based features. Several features in the genome sequence were found to influence protein abundance including codon usage as well as 3' UTR length and structure. Collectively, our studies provide insights into the regulation of the proteome over a diel cycle as well as the relationships between transcriptional and translational programs in the widespread marine green alga Micromonas. %B PloS one %V 11 %P e0155839 %8 jan %G eng %U http://dx.doi.org/10.1371/journal.pone.0155839 %R 10.1371/journal.pone.0155839 %0 Journal Article %J Frontiers in Marine Science %D 2016 %T P- and n-depletion trigger similar cellular responses to promote senescence in eukaryotic phytoplankton %A Rokitta, Sebastian D. %A von Dassow, Peter %A Rost, Björn %A John, Uwe %K 2016 %K rcc1217 %K RCC126 %B Frontiers in Marine Science %V 3 %8 jun %G eng %U http://journal.frontiersin.org/article/10.3389/fmars.2016.00109 http://journal.frontiersin.org/Article/10.3389/fmars.2016.00109/abstract %R 10.3389/fmars.2016.00109 %0 Journal Article %J Journal of Phycology %D 2016 %T Paradoxical effects of temperature and solar irradiance on the photodegradation state of killed phytoplankton %A Amiraux, Remi %A Jeanthon, Christian %A Vaultier, Frédéric %A Rontani, Jean-François %E Mock, T. %K 2016 %K rcc2022 %X The aim of this paper was to study the effects of temperature and irradiance on the photodegradation state of killed phytoplankton cells. For this purpose, killed cells of the diatom Chaetoceros neogracilis RCC2022 were irradiated (PAR radiations) at 36 and 446 J. s(-1.) m(-2) (for a same cumulative dose of irradiation energy) and at two temperatures (7 and 17°C). Analyses of specific lipid tracers (fatty acids and sterols) revealed that low temperatures and irradiances increased photooxidative damages of monounsaturated lipids (i.e. palmitoleic acid, cholesterol and campesterol). The high efficiency of type II photosensitized degradation processes was attributed to: (i) the relative preservation of the sensitizer (chlorophyll) at low irradiances allowing a longer production of singlet oxygen and (ii) the slow diffusion rate of singlet oxygen through membranes at low temperatures inducing more damages. Conversely, high temperatures and irradiances induced (i) a rapid degradation of the photosensitizer and a loss of singlet oxygen by diffusion outside the membranes (limiting type II photosensitized oxidation), and (ii) intense autoxidation processes degrading unsaturated cell lipids and oxidation products used as photodegradation tracers. Our results may likely explain the paradoxical relationship observed in situ between latitude and photodegradation state of phytoplankton cells. This article is protected by copyright. All rights reserved. %B Journal of Phycology %V 52 %P 475–485 %8 jun %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/26992328 http://doi.wiley.com/10.1111/jpy.12410 %R 10.1111/jpy.12410 %0 Journal Article %J Journal of Phycology %D 2016 %T Photosynthetic pigments of oceanic Chlorophyta belonging to prasinophytes clade VII %A Lopes dos Santos, Adriana %A Gourvil, Priscillia %A Rodriguez-Hernandez, Francisco %A Garrido, José Luis %A Vaulot, Daniel %K 2016 %K MACUMBA %K rcc %K RCC1124 %K RCC15 %K RCC1871 %K RCC2337 %K RCC2339 %K RCC287 %K RCC3374 %K RCC3376 %K RCC3402 %K RCC719 %K RCC856 %K RCC857 %K RCC996 %K RCC998 %K RCC?o?dd %K SBR$_\textrmP$hyto$_\textrmD$IPO %K sbr?hyto$_\textrmd$ipo %X The ecological importance and diversity of pico/ nanoplanktonic algae remains poorly studied in marine waters, in part because many are tiny and without distinctive morphological features. Amongst green algae, Mamiellophyceae such as Micromonas or Bathycoccus are dominant in coastal waters while prasinophytes clade VII, yet not formerly described, appear to be major players in open oceanic waters. The pigment composition of 14 strains representative of different subclades of clade VII was analyzed using a method that improves the separation of loroxanthin and neoxanthin. All the prasinophytes clade VII analyzed here showed a pigment composition similar to that previously reported for RCC287 corresponding to pigment group prasino-2A. However, we detected in addition astaxanthin for which it is the first report in prasinophytes. Among the strains analyzed, the pigment signature is qualitatively similar within subclades A and B. By contrast, RCC3402 from subclade C (Picocystis) lacks loroxanthin, astaxanthin, and antheraxanthin but contains alloxanthin, diatoxanthin, and monadoxanthin that are usually found in diatoms or cryptophytes. For subclades A and B, loroxanthin was lowest at highest light irradiance suggesting a light-harvesting role of this pigment in clade VII as in Tetraselmis. %B Journal of Phycology %V 52 %P 148–155 %G eng %R 10.1111/jpy.12376 %0 Journal Article %J Perspectives in Phycology %D 2016 %T Phylogenetic diversity and ecology of green micro algae in marine systems %A Tragin, M %A Lopes dos Santos, Adriana %A Christen, R. %A Vaulot, D. %K 2016 %K ? No DOI found %K rcc %K sbr?hyto$_\textrmd$ipo %B Perspectives in Phycology %V in press %G eng %0 Journal Article %J Journal of Phycology %D 2016 %T Pseudo-nitzschia arctica sp. nov., a new cold-water cryptic Pseudo-nitzschia species within the P. pseudodelicatissima complex %A Percopo, Isabella %A Ruggiero, Maria Valeria %A Balzano, Sergio %A Gourvil, Priscillia %A Lundholm, Nina %A Siano, Raffaele %A Tammilehto, Anna %A Vaulot, Daniel %A Sarno, Diana %E Mock, T. %K RCC2002 %K RCC2004 %K RCC2005 %K RCC2517 %X A new nontoxic Pseudo-nitzschia species belonging to the P. pseudodelicatissima complex, P. arctica, was isolated from different areas of the Arctic. The erection of P. arctica is mainly supported by molecular data, since the species shares identical ultrastructure with another species in the complex, P. fryxelliana, and represents a new case of crypticity within the genus. Despite their morphological similarity, the two species are not closely related in phylogenies based on LSU, ITS and rbcL. Interestingly, P. arctica is phylogenetically most closely related to P. granii and P. subcurvata, from which the species is, however, morphologically different. P. granii and P. subcurvata lack the central larger interspace which is one of the defining features of the P. pseudodelicatissima complex. The close genetic relationship between P. arctica and the two species P. granii and P. subcurvata is demonstrated by analysis of the secondary structure of ITS2 which revealed no compensatory base changes, two hemi-compensatory base changes, and two deletions in P. arctica with respect to the other two species. These findings emphasize that rates of morphological differentiation, molecular evolution and speciation are often incongruent for Pseudo-nitzschia species, resulting in a restricted phylogenetic value for taxonomic characters used to discriminate species. The description of a new cryptic species, widely distributed in the Arctic and potentially representing an endemic component of the Arctic diatom flora, reinforces the idea of the existence of noncosmopolitan Pseudo-nitzschia species and highlights the need for combined morphological and molecular analyses to assess the distributional patterns of phytoplankton species. %B Journal of Phycology %V 52 %P 184–199 %8 apr %G eng %U http://doi.wiley.com/10.1111/jpy.12395 %R 10.1111/jpy.12395 %0 Journal Article %J Frontiers in Microbiology %D 2016 %T Recent reticulate evolution in the ecologically dominant lineage of coccolithophores %A Bendif, El Mahdi %A Probert, Ian %A Díaz-Rosas, Francisco %A Thomas, Daniela %A van den Engh, Ger %A Young, Jeremy R. %A von Dassow, Peter %K 2016 %K coccolithophores %K cyto-nuclear discordance %K diversity %K Emiliania %K evolution %K Gephyrocapsa %K introgressive hybridization %K rcc %K RCC4032 %K RCC4033 %K RCC4034 %K RCC4035 %K RCC4036 %K Reticulofenestra %K sbr?hyto %B Frontiers in Microbiology %V 7 %8 may %G eng %U http://journal.frontiersin.org/article/10.3389/fmicb.2016.00784 http://journal.frontiersin.org/Article/10.3389/fmicb.2016.00784/abstract %R 10.3389/fmicb.2016.00784 %0 Journal Article %J Scientific Reports %D 2016 %T Survey of the green picoalga Bathycoccus genomes in the global ocean %A Vannier, Thomas %A Leconte, Jade %A Seeleuthner, Yoann %A Mondy, Samuel %A Pelletier, Eric %A Aury, Jean-Marc %A de Vargas, Colomban %A Sieracki, Michael %A Iudicone, Daniele %A Vaulot, Daniel %A Wincker, Patrick %A Jaillon, Olivier %K 2016 %K RCC1105 %K RCC715 %K RCC716 %K sbr?hyto$_\textrmd$ipo %K sbr?hyto?ppo %B Scientific Reports %V 6 %P 37900 %8 dec %G eng %U http://www.nature.com/articles/srep37900 %R 10.1038/srep37900 %0 Journal Article %J The ISME Journal %D 2015 %T Effects of low temperature on tropical and temperate isolates of marine Synechococcus %A Varkey, Deepa %A Mazard, Sophie %A Ostrowski, Martin %A Tetu, Sasha G %A Haynes, Paul %A Paulsen, Ian T %K rcc %B The ISME Journal %P 1–12 %G eng %U http://www.nature.com/doifinder/10.1038/ismej.2015.179 %R 10.1038/ismej.2015.179 %0 Journal Article %J Molecular biology and evolution %D 2015 %T Intron invasions trace algal speciation and reveal nearly identical Arctic and Antarctic Micromonas populations. %A Simmons, Melinda P %A Bachy, Charles %A Sudek, Sebastian %A van Baren, Marijke J %A Sudek, Lisa %A Ares, Manuel %A Worden, Alexandra Z %K rcc %X Spliceosomal introns are a hallmark of eukaryotic genes that are hypothesized to play important roles in genome evolution but have poorly understood origins. Although most introns lack sequence homology to each other, recently new families of spliceosomal introns that are repeated hundreds of times in individual genomes have been discovered in a few organisms. The prevalence and conservation of these introner elements (IEs) or introner-like elements (ILEs) in other taxa, as well as their evolutionary relationships to regular spliceosomal introns, are still unknown. Here, we systematically investigate introns in the widespread marine green alga Micromonas and report new families of IEs, numerous intron presence-absence polymorphisms, and potential intron insertion hot-spots. The new families enabled identification of conserved IE secondary structure features and establishment of a novel general model for repetitive intron proliferation across genomes. Despite shared secondary structure, the IE families from each Micromonas lineage bear no obvious sequence similarity to those in the other lineages, suggesting their appearance is intimately linked with the process of speciation. Two of the new IE families come from an Arctic culture (Micromonas Clade E2) isolated from a polar region where this alga is increasing in abundance due to climate change. The same two families were detected in metagenomic data from Antarctica - a system where Micromonas has never before been reported. Strikingly high identity between the Arctic isolate and Antarctic coding sequences that flank the IEs suggests connectivity between populations in the two polar systems that we postulate occurs through deep-sea currents. Recovery of Clade E2 sequences in North Atlantic Deep Waters beneath the Gulf Stream supports this hypothesis. Our work illuminates the dynamic relationships between an unusual class of repetitive introns, genome evolution, speciation and global distribution of this sentinel marine alga. %B Molecular biology and evolution %8 may %G eng %U http://mbe.oxfordjournals.org/cgi/content/long/msv122v1 %R 10.1093/molbev/msv122 %0 Journal Article %J Protist %D 2015 %T Morphological and phylogenetic characterization of new gephyrocapsa isolates suggests introgressive hybridization in the Emiliania/Gephyrocapsa complex (haptophyta) %A Bendif, El Mahdi %A Probert, Ian %A Young, Jeremy R. %A von Dassow, Peter %K 2015 %K coccolithophores %K Emiliania huxleyi %K Gephyrocapsa muellerae %K Gephyrocapsa oceanica %K hybridization %K phylogeny. %K rcc %K RCC1281 %K RCC1282 %K RCC1284 %K RCC1286 %K RCC1292 %K RCC1300 %K RCC1305 %K RCC1307 %K RCC1316 %K RCC1317 %K RCC1318 %K RCC1319 %K RCC1320 %K RCC1562 %K RCC1839 %K RCC3370 %K RCC3862 %K RCC3898 %K species concept %X The coccolithophore genus Gephyrocapsa contains a cosmopolitan assemblage of pelagic species, including the bloom-forming Gephyrocapsa oceanica, and is closely related to the emblematic coccolithophore Emiliania huxleyi within the Noëlaerhabdaceae. These two species have been extensively studied and are well represented in culture collections, whereas cultures of other species of this family are lacking. We report on three new strains of Gephyrocapsa isolated into culture from samples from the Chilean coastal upwelling zone using a novel flow cytometric single-cell sorting technique. The strains were characterized by morphological analysis using scanning electron microscopy and phylogenetic analysis of 6 genes (nuclear 18S and 28S rDNA, plastidial 16S and tufA, and mitochondrial cox1 and cox3 genes). Morphometric features of the coccoliths indicate that these isolates are distinct from G. oceanica and best correspond to G. muellerae. Surprisingly, both plastidial and mitochondrial gene phylogenies placed these strains within the E. huxleyi clade and well separated from G. oceanica isolates, making Emiliania appear polyphyletic. The only nuclear sequence difference, 1bp in the 28S rDNA region, also grouped E. huxleyi with the new Gephyrocapsa isolates and apart from G. oceanica. Specifically, the G. muellerae morphotype strains clustered with the mitochondrial β clade of E. huxleyi, which, like G. muellerae, has been associated with cold (temperate and sub-polar) waters. Among putative evolutionary scenarios that could explain these results we discuss the possibility that E. huxleyi is not a valid taxonomic unit, or, alternatively the possibility of past hybridization and introgression between each E. huxleyi clade and older Gephyrocapsa clades. In either case, the results support the transfer of Emiliania to Gephyrocapsa. These results have important implications for relating morphological species concepts to ecological and evolutionary units of diversity. %B Protist %V 166 %P 323–336 %G eng %U http://www.sciencedirect.com/science/article/pii/S1434461015000243 %R 10.1016/j.protis.2015.05.003 %0 Journal Article %J Aquatic Microbial Ecology %D 2015 %T New lipid envelope-containing dsDNA virus isolates infecting Micromonas pusilla reveal a separate phylogenetic group %A Martínez Martínez, J %A Boere, A %A Gilg, I %A van Lent, Jwm %A Witte, Hj %A van Bleijswijk, Jdl %A Brussaard, Cpd %K characterization %K micromonas pusilla %K ncldv %K phycodnaviridae %K rcc %K RCC?o?dd %K virus diversity %X Viral infection of phytoplankton has major implications for biochemical and energy cycles, community dynamics, and microbial evolution in the marine environment. The non-bloom forming picoplankter Micromonas pusilla, a significant component of the plankton community worldwide, is known to be susceptible to infection by both dsDNA and dsRNA viruses. Logically, comprehensive knowledge of the ecology of M. pusilla requires a better understanding of the div - ersity and infection mechanisms of their viruses. Here, we investigated 19 new M. pusilla-specific viruses (MpVs) isolated from different locations and years. We performed partial characterization of those MpVs including structural characteristics, genome size, phylogenetic analysis based on partial DNA polymerase gene sequences, host range, and stability at different temperatures and upon exposure to chloroform. Combined, these characteristics allowed classification of the MpVs into 2 groups. Exposure to chloroform led to loss of infectivity by all MpVs in one group, which sug- gests the presence of an outer lipid envelope. In addition, all except one of the members in that group formed a monophylogenetic clade that was distinct from all other MpV isolates. The distinc- tive characteristics of the 2 MpV groups suggest different infection strategies, which may have im- portant implications for the ecology of both host and virus populations in the environment. Knowl- edge gained from our study adds value to the MpV isolates as a scientific resource as it will aid in developing and testing in the laboratory new hypotheses about the ecological and biogeochemical implications of M. pusilla viral infection in the environment %B Aquatic Microbial Ecology %V 74 %P 17–28 %G eng %U http://www.int-res.com/abstracts/ame/v74/n1/p17-28/ %R 10.3354/ame01723 %0 Journal Article %J Molecular Ecology Resources %D 2015 %T PhytoREF: a reference database of the plastidial 16S rRNA gene of photosynthetic eukaryotes with curated taxonomy %A Decelle, Johan %A Romac, Sarah %A Stern, Rowena F. %A Bendif, El Mahdi %A Zingone, Adriana %A Audic, Stéphane %A Guiry, Michael D. %A Guillou, Laure %A Tessier, Désiré %A Le Gall, Florence %A Gourvil, Priscillia %A dos Santos, Adriana Lopes %A Probert, Ian %A Vaulot, Daniel %A de Vargas, Colomban %A Christen, Richard %K 2015 %K MACUMBA %K rcc %K RCC?o?dd %K SBR$_\textrmP$hyto$_\textrmD$IPO %K SBR$_\textrmP$hyto$_\textrmE$PPO %K sbr?hyto$_\textrmd$ipo %K sbr?hyto?ppo %X Photosynthetic eukaryotes have a critical role as the main producers in most ecosystems of the biosphere. The ongo- ing environmental metabarcoding revolution opens the perspective for holistic ecosystems biological studies of these organisms, in particular the unicellular microalgae that often lack distinctive morphological characters and have complex life cycles. To interpret environmental sequences, metabarcoding necessarily relies on taxonomically curated databases containing reference sequences of the targeted gene (or barcode) from identified organisms. To date, no such reference framework exists for photosynthetic eukaryotes. In this study, we built the PhytoREF data- base that contains 6490 plastidial 16S rDNA reference sequences that originate from a large diversity of eukaryotes representing all known major photosynthetic lineages. We compiled 3333 amplicon sequences available from public databases and 879 sequences extracted from plastidial genomes, and generated 411 novel sequences from cultured marine microalgal strains belonging to different eukaryotic lineages. A total of 1867 environmental Sanger 16S rDNA sequences were also included in the database. Stringent quality filtering and a phylogeny-based taxonomic classifica- tion were applied for each 16S rDNA sequence. The database mainly focuses on marine microalgae, but sequences from land plants (representing half of the PhytoREF sequences) and freshwater taxa were also included to broaden the applicability of PhytoREF to different aquatic and terrestrial habitats. PhytoREF, accessible via a web interface (http://phytoref.fr), is a new resource in molecular ecology to foster the discovery, assessment and monitoring of the diversity of photosynthetic eukaryotes using high-throughput sequencing. %B Molecular Ecology Resources %V 15 %P 1435–1445 %G eng %U http://doi.wiley.com/10.1111/1755-0998.12401 %R 10.1111/1755-0998.12401 %0 Journal Article %J Cytometry %D 2014 %T An improved protocol for flow cytometry analysis of phytoplankton cultures and natural samples %A Marie, D %A Rigaut-Jalabert, F %A Vaulot, D %K ASSEMBLE %K MACUMBA %K RCC100 %K RCC1085 %K RCC114 %K RCC156 %K RCC168 %K rcc174 %K RCC180 %K RCC190 %K RCC263 %K RCC365 %K RCC400 %K RCC432 %K RCC446 %K RCC475 %K RCC480 %K RCC504 %K RCC745 %K RCC91 %K RCC?o?dd %K SBR$_\textrmP$hyto$_\textrmD$PO %X Preservation of cells, choice of fixative, storage, and thawing conditions are recurrent issues for the analysis of phytoplankton by flow cytometry. We examined the effects of addition of the surfactant Pluronic F68 to glutaraldehyde-fixed photosynthetic organisms in cultures and natural samples. In particular, we examined cell losses and modifications of side scatter (a proxy of cell size) and fluorescence of natural pigments. We found that different marine phytoplankton species react differently to the action of Pluronic F68. In particular, photosynthetic prokaryotes are less sensitive than eukaryotes. Observed cell losses may result from cell lysis or from cell adhesion to the walls of plastic tubes that are commonly used for flow cytometry analysis. The addition of the surfactant, Pluronic F68, has a positive effect on cells for long-term storage. We recommend to modify current protocols for preservation of natural marine planktonic samples, by fixing them with glutaraldehyde 0.25% (final concentration) and adding Pluronic F68 at a final concentration of 0.01% in the samples before preservation. Pluronic F68 also appears effective for preserving samples without fixation for subsequent sorting, e.g. for molecular biology analyses. (c) 2014 International Society for Advancement of Cytometry %B Cytometry %V 85 %P 962–968 %G eng %R 10.1002/cyto.a.22517 %0 Journal Article %J Proceedings of the National Academy of Sciences of the United States of America %D 2014 %T Marine algae and land plants share conserved phytochrome signaling systems %A Duanmu, Deqiang %A Bachy, Charles %A Sudek, Sebastian %A Wong, Chee-Hong %A Jimenez, Valeria %A Rockwell, Nathan C %A Martin, Shelley S %A Ngan, Chew Yee %A Reistetter, Emily N %A van Baren, Marijke J %A Price, Dana C %A Wei, Chia-Lin %A Reyes-Prieto, Adrian %A Lagarias, J Clark %A Worden, Alexandra Z %K Micromonas %K rcc %X Phytochrome photosensors control a vast gene network in streptophyte plants, acting as master regulators of diverse growth and developmental processes throughout the life cycle. In contrast with their absence in known chlorophyte algal genomes and most sequenced prasinophyte algal genomes, a phytochrome is found in Micromonas pusilla, a widely distributed marine picoprasinophyte (¡2 µm cell diameter). Together with phytochromes identified from other prasinophyte lineages, we establish that prasinophyte and streptophyte phytochromes share core light-input and signaling-output domain architectures except for the loss of C-terminal response regulator receiver domains in the streptophyte phytochrome lineage. Phylogenetic reconstructions robustly support the presence of phytochrome in the common progenitor of green algae and land plants. These analyses reveal a monophyletic clade containing streptophyte, prasinophyte, cryptophyte, and glaucophyte phytochromes implying an origin in the eukaryotic ancestor of the Archaeplastida. Transcriptomic measurements reveal diurnal regulation of phytochrome and bilin chromophore biosynthetic genes in Micromonas. Expression of these genes precedes both light-mediated phytochrome redistribution from the cytoplasm to the nucleus and increased expression of photosynthesis-associated genes. Prasinophyte phytochromes perceive wavelengths of light transmitted farther through seawater than the red/far-red light sensed by land plant phytochromes. Prasinophyte phytochromes also retain light-regulated histidine kinase activity lost in the streptophyte phytochrome lineage. Our studies demonstrate that light-mediated nuclear translocation of phytochrome predates the emergence of land plants and likely represents a widespread signaling mechanism in unicellular algae. %B Proceedings of the National Academy of Sciences of the United States of America %V 111 %P 15827–15832 %G eng %U http://www.pnas.org/content/111/44/15827.abstract %R 10.1073/pnas.1416751111 %0 Journal Article %J PLoS biology %D 2014 %T The Marine Microbial Eukaryote Transcriptome Sequencing Project (MMETSP): illuminating the functional diversity of eukaryotic life in the oceans through transcriptome sequencing %A Keeling, Patrick J %A Burki, Fabien %A Wilcox, Heather M %A Allam, Bassem %A Allen, Eric E %A Amaral-Zettler, Linda A %A Armbrust, E Virginia %A Archibald, John M %A Bharti, Arvind K %A Bell, Callum J %A Beszteri, Bank %A Bidle, Kay D %A Cameron, Connor T %A Campbell, Lisa %A Caron, David A %A Cattolico, Rose Ann %A Collier, Jackie L %A Coyne, Kathryn %A Davy, Simon K %A Deschamps, Phillipe %A Dyhrman, Sonya T %A Edvardsen, Bente %A Gates, Ruth D %A Gobler, Christopher J %A Greenwood, Spencer J %A Guida, Stephanie M %A Jacobi, Jennifer L %A Jakobsen, Kjetill S %A James, Erick R %A Jenkins, Bethany %A John, Uwe %A Johnson, Matthew D %A Juhl, Andrew R %A Kamp, Anja %A Katz, Laura A %A Kiene, Ronald %A Kudryavtsev, Alexander %A Leander, Brian S %A Lin, Senjie %A Lovejoy, Connie %A Lynn, Denis %A Marchetti, Adrian %A McManus, George %A Nedelcu, Aurora M %A Menden-Deuer, Susanne %A Miceli, Cristina %A Mock, Thomas %A Montresor, Marina %A Moran, Mary Ann %A Murray, Shauna %A Nadathur, Govind %A Nagai, Satoshi %A Ngam, Peter B %A Palenik, Brian %A Pawlowski, Jan %A Petroni, Giulio %A Piganeau, Gwenael %A Posewitz, Matthew C %A Rengefors, Karin %A Romano, Giovanna %A Rumpho, Mary E %A Rynearson, Tatiana %A Schilling, Kelly B %A Schroeder, Declan C %A Simpson, Alastair G B %A Slamovits, Claudio H %A Smith, David R %A Smith, G Jason %A Smith, Sarah R %A Sosik, Heidi M %A Stief, Peter %A Theriot, Edward %A Twary, Scott N %A Umale, Pooja E %A Vaulot, Daniel %A Wawrik, Boris %A Wheeler, Glen L %A Wilson, William H %A Xu, Yan %A Zingone, Adriana %A Worden, Alexandra Z %K 2014 %K rcc %K SBR$_\textrmP$hyto$_\textrmD$PO %K sbr?hyto$_\textrmd$ipo %X Current sampling of genomic sequence data from eukaryotes is relatively poor, biased, and inadequate to address important questions about their biology, evolution, and ecology; this Community Page describes a resource of 700 transcriptomes from marine microbial eukaryotes to help understand their role in the world's oceans %B PLoS biology %V 12 %P e1001889 %G eng %U http://dx.doi.org/10.1371%252Fjournal.pbio.1001889 %R 10.1371/journal.pbio.1001889 %0 Journal Article %J Current Biology %D 2014 %T A novel protein, ubiquitous in marine phytoplankton, concentrates iron at the cell surface and facilitates uptake %A Morrissey, Joe %A Sutak, Robert %A Paz-Yepes, Javier %A Tanaka, Atsuko %A Moustafa, Ahmed %A Veluchamy, Alaguraj %A Thomas, Yann %A Botebol, Hugo %A Bouget, François-Yves %A McQuaid, Jeffrey B. %A Tirichine, Leila %A Allen, Andrew E. %A Lesuisse, Emmanuel %A Bowler, Chris %K rcc %X Numerous cellular functions including respiration require iron. Plants and phytoplankton must also maintain the iron-rich photosynthetic electron transport chain, which most likely evolved in the iron-replete reducing environments of the Proterozoic ocean [1]. Iron bioavailability has drastically decreased in the contemporary ocean [1], most likely selecting for the evolution of efficient iron acquisition mechanisms among modern phytoplankton. Mesoscale iron fertilization experiments often result in blooms dominated by diatoms [2], indicating that diatoms have adaptations that allow survival in iron-limited waters and rapid multiplication when iron becomes available. Yet the genetic and molecular bases are unclear, as very few iron uptake genes have been functionally characterized from marine eukaryotic phytoplankton, and large portions of diatom iron starvation transcriptomes are genes encoding unknown functions [3–5]. Here we show that the marine diatom Phaeodactylum tricornutum utilizes ISIP2a to concentrate Fe(III) at the cell surface as part of a novel, copper-independent and thermodynamically controlled iron uptake system. ISIP2a is expressed in response to iron limitation several days prior to the induction of ferrireductase activity, and it facilitates significant Fe(III) uptake during the initial response to Fe limitation. ISIP2a is able to directly bind Fe(III) and increase iron uptake when heterologously expressed, whereas knockdown of ISIP2a in P. tricornutum decreases iron uptake, resulting in impaired growth and chlorosis during iron limitation. ISIP2a is expressed by diverse marine phytoplankton, indicating that it is an ecologically significant adaptation to the unique nutrient composition of marine environments. %B Current Biology %V 25 %P 364–371 %8 dec %G eng %U http://www.sciencedirect.com/science/article/pii/S0960982214015632 %R 10.1016/j.cub.2014.12.004 %0 Journal Article %J Molecular Ecology %D 2014 %T Spatiotemporal changes in the genetic diversity of harmful algal blooms caused by the toxic dinoflagellate Alexandrium minutum %A Dia, A %A Guillou, L %A Mauger, S %A Bigeard, E %A Marie, D %A Valero, M %A Destombe, C %K 2014 %K bloom dynamics %K clonality %K linkage disequilibrium %K MACUMBA %K population genetics %K rcc %K RCC?o?dd %K resting cyst %K SBR$_\textrmP$hyto$_\textrmD$PO %K sbr?hyto$_\textrmd$ipo %K sexual reproduction %X Organisms with sexual and asexual reproductive systems benefit from both types of reproduction. Sexual recombination generates new combinations of alleles, whereas clonality favours the spread of the fittest genotype through the entire population. Therefore, the rate of sexual vs. clonal reproduction has a major influence on the demography and genetic structure of natural populations. We addressed the effect of reproductive system on populations of the dinoflagellate Alexandrium minutum. More specifically, we monitored the spatiotemporal genetic diversity during and between bloom events in two estuaries separated by 150 km for two consecutive years. An analysis of population genetic patterns using microsatellite markers revealed surprisingly high genotypic and genetic diversity. Moreover, there was significant spatial and temporal genetic differentiation during and between bloom events. Our results demonstrate that (i) interannual genetic differentiation can be very high, (ii) estuaries are partially isolated during bloom events and (iii) genetic diversity can change rapidly during a bloom event. This rapid genetic change may reflect selective effects that are nevertheless not strong enough to reduce allelic diversity. Thus, sexual reproduction and/or migration may regularly erase any genetic structure produced within estuaries during a bloom event. %B Molecular Ecology %V 23 %P 549–560 %G eng %U http://dx.doi.org/10.1111/mec.12617 %R 10.1111/mec.12617 %0 Journal Article %J Proceedings of the National Academy of Sciences %D 2013 %T Genome structure and metabolic features in the red seaweed Chondrus crispus shed light on evolution of the Archaeplastida %A Collen, Jonas %A Porcel, Betina %A Carré, Wilfrid %A Ball, Steven G %A Chaparro, Cristian %A Tonon, Thierry %A Barbeyron, Tristan %A Michel, Gurvan %A Noel, Benjamin %A Valentin, Klaus %A Elias, Marek %A Artiguenave, François %A Arun, Alok %A Aury, Jean-Marc %A Barbosa-Neto, José F %A Bothwell, John H %A Bouget, François-Yves %A Brillet, Loraine %A Cabello-Hurtado, Francisco %A Capella-Gutiérrez, Salvador %A Charrier, Bénédicte %A Cladière, Lionel %A Cock, J Mark %A Coelho, Susana M %A Colleoni, Christophe %A Czjzek, Mirjam %A Da Silva, Corinne %A Delage, Ludovic %A Denoeud, France %A Deschamps, Philippe %A Dittami, Simon M %A Gabaldón, Toni %A Gachon, Claire M M %A Groisillier, Agnès %A Hervé, Cécile %A Jabbari, Kamel %A Katinka, Michael %A Kloareg, Bernard %A Kowalczyk, Nathalie %A Labadie, Karine %A Leblanc, Catherine %A Lopez, Pascal J %A McLachlan, Deirdre H %A Meslet-Cladiere, Laurence %A Moustafa, Ahmed %A Nehr, Zofia %A Nyvall Collén, Pi %A Panaud, Olivier %A Partensky, Frédéric %A Poulain, Julie %A Rensing, Stefan A %A Rousvoal, Sylvie %A Samson, Gaelle %A Symeonidi, Aikaterini %A Weissenbach, Jean %A Zambounis, Antonios %A Wincker, Patrick %A Boyen, Catherine %K RCC299 %X Red seaweeds are key components of coastal ecosystems and are economically important as food and as a source of gelling agents, but their genes and genomes have received little attention. Here we report the sequencing of the 105-Mbp genome of the florideophyte Chondrus crispus (Irish moss) and the annotation of the 9,606 genes. The genome features an unusual structure characterized by gene-dense regions surrounded by repeat-rich regions dominated by transposable elements. Despite its fairly large size, this genome shows features typical of compact genomes, e.g., on average only 0.3 introns per gene, short introns, low median distance between genes, small gene families, and no indication of large-scale genome duplication. The genome also gives insights into the metabolism of marine red algae and adaptations to the marine environment, including genes related to halogen metabolism, oxylipins, and multicellularity (microRNA processing and transcription factors). Particularly interesting are features related to carbohydrate metabolism, which include a minimalistic gene set for starch biosynthesis, the presence of cellulose synthases acquired before the primary endosymbiosis showing the polyphyly of cellulose synthesis in Archaeplastida, and cellulases absent in terrestrial plants as well as the occurrence of a mannosylglycerate synthase potentially originating from a marine bacterium. To explain the observations on genome structure and gene content, we propose an evolutionary scenario involving an ancestral red alga that was driven by early ecological forces to lose genes, introns, and intergenetic DNA; this loss was followed by an expansion of genome size as a consequence of activity of transposable elements. %B Proceedings of the National Academy of Sciences %V 110 %P 5247–5252 %G eng %U http://www.pnas.org/content/110/13/5247.abstract %R 10.1073/pnas.1221259110 %0 Journal Article %J Environmental Microbiology %D 2013 %T pico-PLAZA, a genome database of microbial photosynthetic eukaryotes %A Vandepoele, Klaas %A Van Bel, Michiel %A Richard, Guilhem %A Van Landeghem, Sofie %A Verhelst, Bram %A Moreau, Hervé %A Van de Peer, Yves %A Grimsley, Nigel %A Piganeau, Gwenael %K Micromonas %K rcc %X With the advent of next generation genome sequencing, the number of sequenced algal genomes and transcriptomes is rapidly growing. Although a few genome portals exist to browse individual genome sequences, exploring complete genome information from multiple species for the analysis of user-defined sequences or gene lists remains a major challenge. pico-PLAZA is a web-based resource (http://bioinformatics.psb.ugent.be/pico-plaza/) for algal genomics that combines different data types with intuitive tools to explore genomic diversity, perform integrative evolutionary sequence analysis and study gene functions. Apart from homologous gene families, multiple sequence alignments, phylogenetic trees, Gene Ontology, InterPro and text-mining functional annotations, different interactive viewers are available to study genome organization using gene collinearity and synteny information. Different search functions, documentation pages, export functions and an extensive glossary are available to guide non-expert scientists. To illustrate the versatility of the platform, different case studies are presented demonstrating how pico-PLAZA can be used to functionally characterize large-scale EST/RNA-Seq data sets and to perform environmental genomics. Functional enrichments analysis of 16 Phaeodactylum tricornutum transcriptome libraries offers a molecular view on diatom adaptation to different environments of ecological relevance. Furthermore, we show how complementary genomic data sources can easily be combined to identify marker genes to study the diversity and distribution of algal species, for example in metagenomes, or to quantify intraspecific diversity from environmental strains. %B Environmental Microbiology %V 15 %P 2147–2153 %G eng %U http://dx.doi.org/10.1111/1462-2920.12174 %R 10.1111/1462-2920.12174 %0 Journal Article %J Nucleic Acids Research %D 2013 %T The protist ribosomal reference database (PR2): a catalog of unicellular eukaryote small SubUnit rRNA sequences with curated taxonomy %A Guillou, Laure %A Bachar, Dipankar %A Audic, Stéphane %A Bass, David %A Berney, Cedric %A Bittner, Lucie %A Boutte, Christophe %A Burgaud, Gaetan %A de Vargas, Colomban %A Decelle, Johan %A del Campo, Javier %A Dolan, John %A Dunthorn, Micah %A Bente, Edvardsen %A Holzmann, Maria %A Kooistra, Wiebe H C F %A Lara, Enrique %A Lebescot, Noan %A Logares, Ramiro %A Mahé, Frédéric %A Massana, Ramon %A Montresor, Marina %A Morard, Raphael %A Not, Fabrice %A Pawlowski, Jan %A Probert, Ian %A Sauvadet, Anne-Laure %A Siano, Raffaele %A Stoeck, Thorsten %A Vaulot, Daniel %A Zimmermann, Pascal %A Christen, Richard %K 2013 %K rcc %K SBR$_\textrmP$hyto$_\textrmD$PO %K SBR$_\textrmP$hyto$_\textrmE$PPO %K sbr?hyto$_\textrmd$ipo %K sbr?hyto?ppo %B Nucleic Acids Research %V 41 %P D597–D604 %G eng %R 10.1093/nar/gks1160 %0 Journal Article %J The ISME journal %D 2012 %T Composition of the summer photosynthetic pico and nanoplankton communities in the Beaufort Sea assessed by T-RFLP and sequences of the 18S rRNA gene from flow cytometry sorted samples %A Balzano, Sergio %A Marie, Dominique %A Gourvil, Priscillia %A Vaulot, Daniel %K 2012 %K ASSEMBLE %K Chaetoceros %K MALINA %K Pyramimonas %K rcc %K SBR$_\textrmP$hyto$_\textrmD$PO %K sbr?hyto$_\textrmd$ipo %K Souchotheque %X The composition of photosynthetic pico and nanoeukaryotes was investigated in the North East Pacific and the Arctic Ocean with special emphasis on the Beaufort Sea during the MALINA cruise in summer 2009. Photosynthetic populations were sorted using flow cytometry based on their size and pigment fluorescence. Diversity of the sorted photosynthetic eukaryotes was determined using terminal-restriction fragment length polymorphism analysis and cloning/sequencing of the 18S ribosomal RNA gene. Picoplankton was dominated by Mamiellophyceae, a class of small green algae previously included in the prasinophytes: in the North East Pacific, the contribution of an Arctic Micromonas ecotype increased steadily northward becoming the only taxon occurring at most stations throughout the Beaufort Sea. In contrast, nanoplankton was more diverse: North Pacific stations were dominated by Pseudo-nitzschia sp. whereas those in the Beaufort Sea were dominated by two distinct Chaetoceros species as well as by Chrysophyceae, Pelagophyceae and Chrysochromulina spp.. This study confirms the importance of Arctic Micromonas within picoplankton throughout the Beaufort Sea and demonstrates that the photosynthetic picoeukaryote community in the Arctic is much less diverse than at lower latitudes. Moreover, in contrast to what occurs in warmer waters, most of the key pico- and nanoplankton species found in the Beaufort Sea could be successfully established in culture. %B The ISME journal %V 6 %P 1480–1498 %G eng %R 10.1038/ismej.2011.213 %0 Journal Article %J Biogeosciences %D 2012 %T Diversity of cultured photosynthetic flagellates in the North East Pacific and Arctic Oceans in summer %A Balzano, Sergio %A Gourvil, Priscillia %A Siano, Raffaele %A Chanoine, Mélanie %A Marie, Dominique %A Lessard, Sylvie %A Sarno, Diana %A Vaulot, Daniel %K 2012 %K ASSEMBLE %K MACUMBA %K MALINA %K rcc %K SBR$_\textrmP$hyto$_\textrmD$PO %K sbr?hyto$_\textrmd$ipo %B Biogeosciences %V 9 %P 4553–4571 %G eng %R 10.5194/bg-9-4553-2012 %0 Journal Article %J PLoS ONE %D 2012 %T Evaluating the ribosomal internal transcribed spacer (ITS) as a candidate dinoflagellate barcode marker %A Stern, Rowena F %A Andersen, Robert A %A Jameson, Ian %A Küpper, Frithjof C %A Coffroth, Mary-Alice %A Vaulot, Daniel %A Gall, Florence Le %A Veron, Benoit %A Brand, Jerry J %A Skelton, Hayley %A Kasai, Fumai %A Lilly, Emily L %A Keeling, Patrick J %K 2012 %K ASSEMBLE %K Barcoding %K ITS %K rcc %K SBR$_\textrmP$hyto$_\textrmD$PO %K sbr?hyto$_\textrmd$ipo %B PLoS ONE %V 7 %P e42780 %G eng %U http://www.plosone.org/article/info%253Adoi%252F10.1371%252Fjournal.pone.0042780 %R 10.1371/journal.pone.0042780 %0 Journal Article %J Protist %D 2012 %T Lotharella reticulosa sp. nov.: A highly reticulated network forming chlorarachniophyte from the mediterranean sea %A Ota, Shuhei %A Vaulot, Daniel %K Chlorarachniophytes %K Lotharella %K Mediterranean Sea %K RCC375 %K RCC376 %K Taxonomy. %X A new chlorarachniophyte Lotharella reticulosa sp. nov. is described from a culture isolated from the Mediterranean Sea. This strain is maintained as strain RCC375 at the Roscoff Culture Collection, France. This species presents a multiphasic life cycle: vegetative cells of this species were observed to be coccoid, but amoeboid cells with filopodia and globular suspended cells were also present in the life cycle, both of which were not dominant phases. Flagellate cells were also observed but remained very rare in culture. The vegetative cells were 9-16 ??m in diameter and highly vacuolated, containing several green chloroplasts with a projecting pyrenoid, mitochondria, and a nucleus. The chloroplast was surrounded by four membranes possessing a nucleomorph in the periplastidial compartment near the pyrenoid base. According to ultrastructural observations of the pyrenoid and nucleomorph, the present species belongs to the genus Lotharella in the phylum Chlorarachniophyta. This taxonomic placement is consistent with the molecular phylogenetic trees of the 18S rRNA gene and ITS sequences. This species showed a unique colonization pattern. Clusters of cells extended cytoplasmic strands radially. Then, amoeboid cells being born proximately moved distally along the cytoplasmic strand like on a "railway track" Subsequently the amoeboid cell became coccoid near the strand. In this way, daughter cells were dispersed evenly on the substratum. We also observed that the present species regularly formed a structure of filopodial nodes in mid-stage and later-stage cultures, which is a novel phenotype in chlorarachniophytes. The unique colonization pattern and other unique features demonstrate that RCC375 is a new chlorarachniophyte belonging to genus Lotharella, which we describe as Lotharella reticulosa sp. nov. ?? 2011 Elsevier GmbH. %B Protist %V 163 %P 91–104 %G eng %0 Journal Article %J The ISME journal %D 2012 %T Phytoplankton distribution patterns in the northwestern Sargasso Sea revealed by small subunit rRNA genes from plastids %A Treusch, Alexander H %A Demir-Hilton, Elif %A Vergin, Kevin L %A Worden, Alexandra Z %A Carlson, Craig A %A Donatz, Michael G %A Burton, Robert M %A Giovannoni, Stephen J %K Bathycoccus %K CHRYSOPHYCEAE %K key?aper %K Micromonas %K Ostreococcus %K pelagophyceae %K Prasinophyceae %K Prymnesiophyceae %K QPCR %K rcc %K TRFLP %B The ISME journal %V 6 %P 481–492 %G eng %U http://dx.doi.org/10.1038/ismej.2011.117 http://www.nature.com/ismej/journal/vaop/ncurrent/suppinfo/ismej2011117s1.html %R 10.1038/ismej.2011.117 %0 Journal Article %J Nature Geoscience %D 2012 %T Significant silicon accumulation by marine picocyanobacteria %A Baines, Stephen B. %A Twining, Benjamin S. %A Brzezinski, Mark a. %A Krause, Jeffrey W. %A Vogt, Stefan %A Assael, Dylan %A McDaniel, Hannah %K rcc1084 %K RCC1086 %K rcc752 %X The marine silicon cycle is thought to be intimately tied to the carbon cycle through its effect on the growth of diatoms. These unicellular algae form substantial blooms in cold, nutrient-rich waters. Their dense, siliceous cell walls promote the sinking of particulate matter, and all the carbon and nutrients contained therein1. As such, diatoms are thought to be the primary organisms responsible for the low levels of dissolved silicon observed in the surface ocean and the export of mineral silica to depth. Here, we use synchrotron X-ray fluorescence microscopy to determine the elemental composition of individual diatoms and cyanobacterial cells from the eastern equatorial Pacific and the Sargasso Sea.We show that cells of Synechococcus, a small unicellular marine cyanobacterium that dominates in nutrient-depleted waters2, can exhibit cellular ratios of silicon to sulphur, and silicon to phosphorus, approaching those detected in diatoms in the same location. Silicon accumulation was also observed in cultured Synechococcus strains. We estimate that the water column inventory of silicon in Synechococcus can exceed that of diatomsinsomecases.We suggest that picocyanobacteriamay exert a previously unrecognized influence on the oceanic silicon cycle, especially in nutrient-poorwaters. %B Nature Geoscience %V 5 %P 886–891 %G eng %U http://www.nature.com/doifinder/10.1038/ngeo1641 %R 10.1038/ngeo1641 %0 Journal Article %J Marine Ecology Progress Series %D 2012 %T Temperature-dependent growth and photophysiology of prokaryotic and eukaryotic oceanic picophytoplankton %A Kulk, Gemma %A De Vries, Pablo %A Van De Poll, Willem H. %A Visser, Ronald J W %A Buma, Anita G J %K Absorption %K Electron transport rate %K Eukaryotic picophytoplankton %K Growth %K Pigment %K Prochlorococcus %K rcc %K RCC407 %K rcc410 %K RCC879 %K temperature %X ABSTRACT: It is expected that climate change will expand the open oligotrophic oceans by enhanced thermal stratification. Because temperature defines the geographic distribution of picophytoplankton in open-ocean ecosystems and regulates photophysiological responses, it is important to understand how temperature affects picophytoplankton growth and photophysiology. Two prokaryotic and 2 eukaryotic picophytoplankton strains were acclimated to 3 different temperatures, ranging from 16 to 24°C. Temperature-dependent growth and photophysiology were assessed by measurements of specific growth rates, cell size, pigment composition, absorption and electron transport rates. Growth of Prochlorococcus marinus (eMED4), Prochlorococcus sp. (eMIT9313), Ostreococcus sp. (clade B) and Pelagomonas calceolata was positively related to temperature, especially in the prokaryotic strains. Changes in photophysiology included increased light harvesting, increased electron transport and reduced photoinhibition at elevated temperatures. However, the changes related to light harvesting and electron transport could not fully explain the observed difference in growth. This suggests that other processes, such as Calvin cycle activity, are likely to limit growth at sub-optimal temperatures in these picophytoplankton strains. The overall changes in photophysiology during temperature acclimation will possibly allow photosynthesis at higher irradiance intensities, but the genetically defined low temperature tolerances and photosynthetic characteristics of the different ecotypes will likely be more important in determining picophytoplankton (depth) distribution and community composition. %B Marine Ecology Progress Series %V 466 %P 43–55 %G eng %U http://www.int-res.com/abstracts/meps/v466/p43-55/ %R 10.3354/meps09898 %0 Journal Article %J Science %D 2012 %T Unicellular cyanobacterium symbiotic with a single-celled eukaryotic alga %A Thompson, Anne W %A Foster, Rachel A %A Krupke, Andreas %A Carter, Brandon J %A Musat, Niculina %A Vaulot, Daniel %A Kuypers, Marcel M M %A Zehr, Jonathan P %K 2012 %K MicroB3 %K rcc %K SBR$_\textrmP$hyto$_\textrmD$PO %K sbr?hyto$_\textrmd$ipo %X Symbioses between nitrogen (N)2–fixing prokaryotes and photosynthetic eukaryotes are important for nitrogen acquisition in N-limited environments. Recently, a widely distributed planktonic uncultured nitrogen-fixing cyanobacterium (UCYN-A) was found to have unprecedented genome reduction, including the lack of oxygen-evolving photosystem II and the tricarboxylic acid cycle, which suggested partnership in a symbiosis. We showed that UCYN-A has a symbiotic association with a unicellular prymnesiophyte, closely related to calcifying taxa present in the fossil record. The partnership is mutualistic, because the prymnesiophyte receives fixed N in exchange for transferring fixed carbon to UCYN-A. This unusual partnership between a cyanobacterium and a unicellular alga is a model for symbiosis and is analogous to plastid and organismal evolution, and if calcifying, may have important implications for past and present oceanic N2 fixation. %B Science %V 337 %P 1546–1550 %G eng %U http://www.sciencemag.org/content/337/6101/1546.abstract %R 10.1126/science.1222700 %0 Journal Article %J Protist %D 2011 %T Integrative taxonomy of the pavlovophyceae (haptophyta) : a reassessment %A Bendif, E M %A Probert, I %A Hervé, A %A Billard, C %A Goux, D %A Lelong, C %A Cadoret, J P %A Véron, B %K 2011 %K ASSEMBLE %K rcc %K RCC1523 %K rcc1524 %K rcc1525 %K RCC1526 %K RCC1527 %K RCC1528 %K RCC1529 %K RCC1530 %K RCC1531 %K RCC1532 %K RCC1533 %K RCC1534 %K RCC1535 %K RCC1536 %K RCC1537 %K RCC1538 %K RCC1539 %K RCC1540 %K RCC1541 %K RCC1542 %K RCC1543 %K RCC1544 %K RCC1545 %K RCC1546 %K RCC1548 %K RCC1549 %K RCC1551 %K RCC1552 %K RCC1553 %K RCC1554 %K RCC1557 %K SBR$_\textrmP$hyto$_\textrmE$PPO %X The Pavlovophyceae (Haptophyta) contains four genera (Pavlova, Diacronema, Exanthemachrysis and Rebecca) and only thirteen characterised species. Considering the importance of members of this class, we constructed molecular phylogenies inferred from sequencing of ribosomal gene markers with comprehensive coverage of the described diversity and using type strains when available add on culture strains. Moreover, the morphology and ultrastructure of 12 of the described species was re-examined and the pigment signatures of many culture strains were determined. The molecular analysis revealed that sequences of all described species differed, although those of Pavlova gyrans and P. pinguis were nearly identical, these potentially forming a single cryptic species complex. Four well-delineated genetic clades were identified, one of which included species of both Pavlova andDiacronema. Unique combinations of morphological/ultrastructural characters were identified foreach of these clades. The ancestral pigment signature of the Pavlovophyceae consisted of a basic set of pigments plus MV chl cPAV, the latter being entirely absent in the Pavlova + Diacronema clade and supplemented by DV chl cPAV in part of the Exanthemachrysis clade. Based on this combination of characters, we propose a taxonomic revision of the class, with transfer of several Pavlova species to an emended Diacronema genus. The evolution of the class is discussed in the context of the phylogenetic reconstruction presented. %B Protist %V 162 %P 738–761 %G eng %R 10.1016/j.protis.2011.05.001 %0 Journal Article %J Proceedings of the National Academy of Sciences of the United States of America %D 2011 %T Niche of harmful alga Aureococcus anophagefferens revealed through ecogenomics %A Gobler, C J %A Berry, D L %A Dyhrman, S T %A Wilhelm, S W %A Salamov, A %A Lobanov, A V %A Zhang, Y %A Collier, J L %A Wurch, L L %A Kustka, A B %A Dill, B D %A Shah, M %A VerBerkmoes, N C %A Kuo, A %A Terry, A %A Pangilinan, J %A Lindquist, E A %A Lucas, S %A Paulsen, I T %A Hattenrath-Lehmann, T K %A Talmage, S C %A Walker, E A %A Koch, F %A Burson, A M %A Marcoval, M A %A Tang, Y Z %A LeCleir, G R %A Coyne, K J %A Berg, G M %A Bertrand, E M %A Saito, M A %A Gladyshev, V N %A Grigoriev, I V %K brown-tide blooms %K comparative genomics %K eutrophication %K evolution %K genome %K genomics %K long-island %K marine-phytoplankton %K multidrug %K proteins %K proteome %K rcc %K repeat %K responses %K san-francisco bay %K signal-transduction %K transporters %X Harmful algal blooms (HABs) cause significant economic and ecological damage worldwide. Despite considerable efforts, a comprehensive understanding of the factors that promote these blooms has been lacking, because the biochemical pathways that facilitate their dominance relative to other phytoplankton within specific environments have not been identified. Here, biogeochemical measurements showed that the harmful alga Aureococcus anophagefferens outcompeted co-occurring phytoplankton in estuaries with elevated levels of dissolved organic matter and turbidity and low levels of dissolved inorganic nitrogen. We subsequently sequenced the genome of A. anophagefferens and compared its gene complement with those of six competing phytoplankton species identified through metaproteomics. Using an ecogenomic approach, we specifically focused on gene sets that may facilitate dominance within the environmental conditions present during blooms. A. anophagefferens possesses a larger genome (56 Mbp) and has more genes involved in light harvesting, organic carbon and nitrogen use, and encoding selenium-and metal-requiring enzymes than competing phytoplankton. Genes for the synthesis of microbial deterrents likely permit the proliferation of this species, with reduced mortality losses during blooms. Collectively, these findings suggest that anthropogenic activities resulting in elevated levels of turbidity, organic matter, and metals have opened a niche within coastal ecosystems that ideally suits the unique genetic capacity of A. anophagefferens and thus, has facilitated the proliferation of this and potentially other HABs. %B Proceedings of the National Academy of Sciences of the United States of America %V 108 %P 4352–4357 %G eng %R 10.1073/pnas.1016106108 %0 Journal Article %J FEMS Microbiology Ecology %D 2011 %T Whole Genome Amplification (WGA) of marine photosynthetic eukaryote populations %A Lepere, Cecile %A Demura, M %A Kawachi, M %A Romac, S %A Probert, I %A Vaulot, D %K 2011 %K PICOFUNPAC %K rcc %K SBR$_\textrmP$hyto$_\textrmD$PO %K SBR$_\textrmP$hyto$_\textrmE$PPO %K sbr?hyto$_\textrmd$ipo %K sbr?hyto?ppo %B FEMS Microbiology Ecology %V 76 %P 516–523 %G eng %R 10.1111/j.1574-6941.2011.01072.x %0 Journal Article %J Science %D 2009 %T Green evolution and dynamic adaptations revealed by genomes of the marine picoeukaryotes Micromonas %A Worden, A Z %A Lee, J.- H %A Mock, T %A Rouzé, P %A Simmons, M P %A Aerts, A L %A Allen, A E %A Cuvelier, M L %A Derelle, E %A Everett, M V %A Foulon, E %A Grimwood, J %A Gundlach, H %A Henrissat, B %A Napoli, C %A McDonald, S M %A Parker, M S %A Rombauts, S %A Salamov, A %A Von Dassow, P %A Badger, J H %A Coutinho, P M %A Demir, E %A Dubchak, I %A Gentemann, C %A Eikrem, W %A Gready, J E %A John, U %A Lanier, W %A Lindquist, E A %A Lucas, S %A Mayer, K F X %A Moreau, H %A Not, F %A Otillar, R %A Panaud, O %A Pangilinan, J %A Paulsen, I %A Piegu, B %A Poliakov, A %A Robbens, S %A Schmutz, J %A Toulza, E %A Wyss, T %A Zelensky, A %A Zhou, K %A Armbrust, E V %A Bhattacharya, D %A Goodenough, U W %A Van de Peer, Y %A Grigoriev, I V %K rcc %K RCC299 %K RCC827 %K SBR$_\textrmP$hyto$_\textrmD$PO %K SBR$_\textrmP$hyto$_\textrmE$PPO %X The photosynthetic picoeukaryote Micromonas thrives from tropical to polar marine ecosystems and belongs to an anciently diverged sister clade to land plants. We sequenced genomes from two Micromonas isolates (22 Mb, CCMP1545; 21 Mb, RCC299) and the results improve understanding of their ecology and green-lineage evolution. Despite high 18S rDNA sequence identity, only 90% of their predicted genes were shared. Novel intronic repeat elements in CCMP1545, otherwise found only in metagenomic data, and unique riboswitch arrangements emphasized their independent evolutionary paths. Phylogenomic profiles revealed putative ancestral features, but also indicated selection/acquisition processes are actively shaping a ‘unique' gene pool in each differently than ‘core' genes. Current climate-change trajectories are predicted to produce conditions favoring picophytoplankton, making Micromonas potential indicators of biological change in ocean ecosystems. %B Science %V 324 %P 268–272 %G eng %R 10.1126/science.1167222 %0 Journal Article %J Protist %D 2009 %T Partenskyella glossopodia gen. et sp. nov., the first report of chlorarachniophyte that lacks pyrenoid %A Ota, S %A Vaulot, D %A Le Gall, F %A Yabuki, A %A Ishida, K %K 2009 %K rcc %K SBR$_\textrmP$hyto$_\textrmD$PO %K sbr?hyto$_\textrmd$ipo %B Protist %V 160 %P 137–150 %G eng %R 10.1016/j.protis.2008.09.003 %0 Journal Article %J Genome Biology %D 2009 %T Transcriptome analysis of functional differentiation between haploid and diploid cells of Emiliania huxleyi, a globally significant photosynthetic calcifying cell %A von Dassow, Peter %A Ogata, Hiroyuki %A Probert, Ian %A Wincker, Patrick %A Da Silva, Corinne %A Audic, Stéphane %A Claverie, Jean-Michel %A de Vargas, Colomban %K 2009 %K rcc %K RCC1216 %K rcc1217 %K SBR$_\textrmP$hyto$_\textrmE$PPO %K sbr?hyto?ppo %X BACKGROUND:Eukaryotes are classified as either haplontic, diplontic, or haplo-diplontic, depending on which ploidy levels undergo mitotic cell division in the life cycle. Emiliania huxleyi is one of the most abundant phytoplankton species in the ocean, playing an important role in global carbon fluxes, and represents haptophytes, an enigmatic group of unicellular organisms that diverged early in eukaryotic evolution. This species is haplo-diplontic. Little is known about the haploid cells, but they have been hypothesized to allow persistence of the species between the yearly blooms of diploid cells. We sequenced over 38000 Expressed Sequence Tags (ESTs) from haploid and diploid E. huxleyi normalized cDNA libraries to identify genes involved in important processes specific to each life phase (2N calcification or 1N motility), and to better understand the haploid phase of this prominent haplo-diplontic organism.RESULTS:The haploid and diploid transcriptomes showed a dramatic differentiation, with [almost equal to]20% greater transcriptome richness in diploid cells than in haploid cells and only [less than or equal to]50% of transcripts estimated to be common between the two phases. The major functional category of transcripts differentiating haploids included signal transduction and motility genes. Diploid-specific transcripts included Ca2+, H+, and HCO3- pumps. Potential factors differentiating the transcriptomes included haploid-specific Myb transcription factor homologs and an unusual diploid-specific histone H4 homolog.CONCLUSIONS:This study permitted the identification of genes likely involved in diploid-specific biomineralization, haploid-specific motility, and transcriptional control. Greater transcriptome richness in diploid cells suggests they may be more versatile for exploiting a diversity of rich environments whereas haploid cells are intrinsically more streamlined. %B Genome Biology %V 10 %P R114 %G eng %U http://genomebiology.com/2009/10/10/R114 %R 10.1186/gb-2009-10-10-r114 %0 Journal Article %D 2008 %T The diversity of small eukaryotic phytoplankton (¡3 µm) in marine ecosystems %A Vaulot, Daniel %A Eikrem, Wenche %A Viprey, Manon %A Moreau, Hervé %K 2008 %K diversity %K genomics %K Marine ecosystems %K Micro-algae %K picoplankton %K rcc %K sbr?hyto$_\textrmd$ipo %K taxonomy %X Small cells dominate photosynthetic biomass and primary production in many marine ecosystems. Traditionally, picoplankton refers to cells ¡ or =2 microm. Here we extend the size range of the organisms considered to 3 microm, a threshold often used operationally in field studies. While the prokaryotic component of picophytoplankton is dominated by two genera, Prochlorococcus and Synechococcus, the eukaryotic fraction is much more diverse. Since the discovery of the ubiquitous Micromonas pusilla in the early 1950s, just over 70 species that can be ¡3 microm have been described. In fact, most algal classes contain such species. Less than a decade ago, culture-independent approaches (in particular, cloning and sequencing, denaturing gradient gel electrophoresis, FISH) have demonstrated that the diversity of eukaryotic picoplankton is much more extensive than could be assumed from described taxa alone. These approaches revealed the importance of certain classes such as the Prasinophyceae but also unearthed novel divisions such as the recently described picobiliphytes. In the last couple of years, the first genomes of photosynthetic picoplankton have become available, providing key information on their physiological capabilities. In this paper, we discuss the range of methods that can be used to assess small phytoplankton diversity, present the species described to date, review the existing molecular data obtained on field populations, and end up by looking at the promises offered by genomics. %V 32 %P 795–820 %G eng %0 Journal Article %J Aquatic Microbial Ecology %D 2008 %T Effects of temperature on photosynthetic parameters and TEP production in eight species of marine microalgae %A Claquin, Pascal %A Probert, Ian %A Lefebvre, Sébastien %A Veron, Benoit %K 2008 %K rcc %K SBR$_\textrmP$hyto %B Aquatic Microbial Ecology %V 51 %P 1–11 %G eng %R 10.3354/ame01187 %0 Journal Article %J New Phytologist %D 2008 %T New tools for labeling silica in living diatoms %A Descles, J %A Vartanian, M %A El Harrak, A %A Quinet, M %A Bremond, N %A Sapriel, G %A Bibette, J %A Lopez, P J %K 3D-imaging %K BACILLARIOPHYCEAE %K BIOLOGY %K biomineralization %K DEPOSITION %K diatoms %K exocytosis %K FLUORESCENT %K nanopattern %K pH %K phaeodactylum-tricornutum %K PLANTS %K rcc %K THALASSIOSIRA-PSEUDONANA %K ultrastructure %K VESICLE %X Silicon biomineralization is a widespread mechanism found in several kingdoms that concerns both unicellular and multicellular organisms. As a result of genomic and molecular tools, diatoms have emerged as a good model for biomineralization studies and have provided most of the current knowledge on this process. However, the number of techniques available to study its dynamics at the cellular level is still rather limited. Here, new probes were developed specifically to label the pre-existing or the newly synthesized silica frustule of several diatoms species. It is shown that the LysoTracker Yellow HCK-123, which can be used to visualize silica frustules with common filter sets, presents an enhanced signal-to-noise ratio and allows details of the frustules to be imaged without of the use of ionophores. It is also demonstrated that methoxysilane derivatives can be coupled to fluorescein-5-isothiocyanate (FITC) to preferentially label the silica components of living cells. The coupling of labeling procedures might help to address the challenging question of the process of frustule exocytosis. %B New Phytologist %V 177 %P 822–829 %G eng %R 10.1111/j.1469-8137.2007.02303.x %0 Journal Article %J Nature %D 2008 %T The Phaeodactylum genome reveals the evolutionary history of diatom genomes %A Bowler, Chris %A Allen, Andrew E %A Badger, Jonathan H %A Grimwood, Jane %A Jabbari, Kamel %A Kuo, Alan %A Maheswari, Uma %A Martens, Cindy %A Maumus, Florian %A Otillar, Robert P %A Rayko, Edda %A Salamov, Asaf %A Vandepoele, Klaas %A Beszteri, Bank %A Gruber, Ansgar %A Heijde, Marc %A Katinka, Michael %A Mock, Thomas %A Valentin, Klaus %A Verret, Frederic %A Berges, John A %A Brownlee, Colin %A Cadoret, Jean-Paul %A Chiovitti, Anthony %A Choi, Chang Jae %A Coesel, Sacha %A De Martino, Alessandra %A Detter, J Chris %A Durkin, Colleen %A Falciatore, Angela %A Fournet, Jerome %A Haruta, Miyoshi %A Huysman, Marie J J %A Jenkins, Bethany D %A Jiroutova, Katerina %A Jorgensen, Richard E %A Joubert, Yolaine %A Kaplan, Aaron %A Kroger, Nils %A Kroth, Peter G %A La Roche, Julie %A Lindquist, Erica %A Lommer, Markus %A Martin-Jezequel, Veronique %A Lopez, Pascal J %A Lucas, Susan %A Mangogna, Manuela %A McGinnis, Karen %A Medlin, Linda K %A Montsant, Anton %A Secq, Marie-Pierre Oudot-Le %A Napoli, Carolyn %A Obornik, Miroslav %A Parker, Micaela Schnitzler %A Petit, Jean-Louis %A Porcel, Betina M %A Poulsen, Nicole %A Robison, Matthew %A Rychlewski, Leszek %A Rynearson, Tatiana A %A Schmutz, Jeremy %A Shapiro, Harris %A Siaut, Magali %A Stanley, Michele %A Sussman, Michael R %A Taylor, Alison R %A Vardi, Assaf %A von Dassow, Peter %A Vyverman, Wim %A Willis, Anusuya %A Wyrwicz, Lucjan S %A Rokhsar, Daniel S %A Weissenbach, Jean %A Armbrust, E Virginia %A Green, Beverley R %A Van de Peer, Yves %A Grigoriev, Igor V %K 2008 %K rcc %K SBR$_\textrmP$hyto$_\textrmE$PPOdipo %K sbr?hyto?ppo %B Nature %V 456 %P 239–244 %G eng %U http://dx.doi.org/10.1038/nature07410 http://www.nature.com/nature/journal/v456/n7219/suppinfo/nature07410_S1.html %R 10.1038/nature07410 %0 Journal Article %J Biogeosciences %D 2008 %T Picoplankton diversity in the south-east pacific ocean from cultures %A Le Gall, F %A Rigaut-Jalabert, F %A Marie, D %A Garczareck, L %A Viprey, M %A Godet, A %A Vaulot, D %K 2008 %K PICOFUNPAC %K rcc %K SBR$_\textrmP$hyto$_\textrmD$PO %K sbr?hyto$_\textrmd$ipo %K sbr?hyto?app %B Biogeosciences %V 5 %P 203–214 %G eng %R 10.5194/bg-5-203-2008 %0 Journal Article %J Cahiers de Biologie Marine %D 2008 %T Plankton taxonomy in the computer age %A Jouenne, F %A Probert, I %A Vaulot, D %K 2008 %K ? No DOI found %K rcc %K SBR$_\textrmP$hyto$_\textrmD$PO %K sbr?hyto$_\textrmd$ipo %X

Preservation of biodiversity starts with knowledge of biodiversity. Based on this principle, numerous projects combining taxonomy and web-based technologies have developed over the last fifteen years, often with the aim of listing all living organisms described to date. Individual lists have been progressively incorporated into federative projects, such as Species 2000 or the Global Biodiversity Information Facility (GBIF). Nowadays, modern taxonomy is splited up between traditionalism and pragmatism. The Internet can provide new advantages to taxonomy (accessibility and efficiency) without reducing quality. In the future, it would be highly desirable to ba able to publish species descriptions and revisions on permanent web-sites on the model of GENBANK. Biodiversity inventory projects should converge to a very limited number of portals (e.g. Encyclopedia of Life). We illustrate these concepts by presenting Plankton*Net an interactive web site dedicated to the taxonomy and images of plankton.

%B Cahiers de Biologie Marine %V 49 %P 355–367 %G eng %0 Journal Article %J Environmental Microbiology %D 2008 %T Wide genetic diversity of picoplanktonic green algae (Chloroplastida) in the Mediterranean Sea uncovered by a phylum-biased PCR approach %A Viprey, Manon %A Guillou, Laure %A Ferréol, Martial %A Vaulot, Daniel %K 2008 %K rcc %K sbr?hyto$_\textrmd$ipo %X The genetic diversity of picoplanktonic (i.e. cells that can pass through a 3 mum pore-size filter) green algae was investigated in the Mediterranean Sea in late summer by a culture-independent approach. Genetic libraries of the 18S rRNA gene were constructed using two different primer sets. The first set is commonly used to amplify the majority of eukaryotic lineages, while the second was composed of a general eukaryotic forward primer and a reverse primer biased towards the phylum Chloroplastida. A total of 3980 partial environmental sequences were obtained: 1668 using the general eukaryotic primer set and 2312 using the Chloroplastida-biased primer set. Of these sequences, 65 (4%) and 594 (26%) belonged to the Chloroplastida respectively. A 99.5% sequence similarity cut-off value allowed classification of these 659 Chloroplastida sequences into 74 different operational taxonomic units. A majority of the Chloroplastida sequences (99%) belonged to the prasinophytes. In addition to the seven independent prasinophyte lineages previously described, we discovered two new clades (clades VIII and IX), as well as a significant genetic diversity at the species and subspecies levels, notably among the genera Crustomastix, Dolichomastix and Mamiella (Mamiellales), but also within Pyramimonas and Halosphaera (Pyramimonadales). Such diversity within prasinophytes has not previously been observed by cloning approaches, illustrating the power of using targeted primers for clone library construction. Prasinophyte assemblages differed especially in relation to nutrient levels. Micromonas and Ostreococcus were mainly recovered from mesotrophic areas, whereas Mamiella, Crustomastix and Dolichomastix were mostly detected in oligotrophic surface waters. Within genera such as Ostreococcus or Crustomastix for which several clades were observed, depth seemed to be the main factor controlling differential distribution of genotypes. %B Environmental Microbiology %V 10 %P 1804–1822 %G eng %0 Journal Article %J Molecular Biology and Evolution %D 2007 %T The complete chloroplast and mitochondrial DNA sequence of Ostreococcus tauri: organelle genomes of the smallest eukaryote are examples of compaction %A Robbens, S %A Derelle, E %A Ferraz, C %A Wuyts, J %A Moreau, H %A Van de Peer, Y %K rcc %X The complete nucleotide sequence of the mt (mitochondrial) and cp (chloroplast) genomes of the unicellular green alga Ostreococcus tauri has been determined. The mt genome assembles as a circle of 44,237 bp and contains 65 genes. With an overall average length of only 42 bp for the intergenic regions, this is the most gene-dense mt genome of all Chlorophyta. Furthermore, it is characterized by a unique segmental duplication, encompassing 22 genes and covering 44% of the genome. Such a duplication has not been observed before in green algae, although it is also present in the mt genomes of higher plants. The quadripartite cp genome forms a circle of 71,666 bp, containing 86 genes divided over a larger and a smaller single-copy region, separated by 2 inverted repeat sequences. Based on genome size and number of genes, the Ostreococcus cp genome is the smallest known among the green algae. Phylogenetic analyses based on a concatenated alignment of cp, mt, and nuclear genes confirm the position of O. tauri within the Prasinophyceae, an early branch of the Chlorophyta. %B Molecular Biology and Evolution %V 24 %P 956–968 %G eng %U http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=17251180 %0 Journal Article %J Proceedings of the National Academy of Sciences of the United States of America %D 2007 %T The tiny eukaryote \textit{Ostreococcus provides genomic insights into the paradox of plankton speciation %A Palenik, B %A Grimwood, J %A Aerts, A %A Rouzé, P %A Salamov, A %A Putnam, N %A Dupont, C %A Jorgensen, R %A Derelle, E %A Rombauts, S %A Zhou, K %A Otillar, R %A Merchant, S S %A Podell, S %A Gaasterland, T %A Napoli, C %A Gendler, K %A Manuell, A %A Tai, V %A Vallon, O %A Piganeau, G %A Jancek, S %A Heijde, M %A Jabbari, K %A Bowler, C %A Lohr, M %A Robbens, S %A Werner, G %A Dubchak, I %A Pazour, G J %A Ren, Q %A Paulsen, I %A Delwiche, C %A Schmutz, J %A Rokhsar, D %A Van de Peer, Y %A Moreau, H %A Grigoriev, I V %K rcc %X The smallest known eukaryotes, at approximately 1-mum diameter, are Ostreococcus tauri and related species of marine phytoplankton. The genome of Ostreococcus lucimarinus has been completed and compared with that of O. tauri. This comparison reveals surprising differences across orthologous chromosomes in the two species from highly syntenic chromosomes in most cases to chromosomes with almost no similarity. Species divergence in these phytoplankton is occurring through multiple mechanisms acting differently on different chromosomes and likely including acquisition of new genes through horizontal gene transfer. We speculate that this latter process may be involved in altering the cell-surface characteristics of each species. In addition, the genome of O. lucimarinus provides insights into the unique metal metabolism of these organisms, which are predicted to have a large number of selenocysteine-containing proteins. Selenoenzymes are more catalytically active than similar enzymes lacking selenium, and thus the cell may require less of that protein. As reported here, selenoenzymes, novel fusion proteins, and loss of some major protein families including ones associated with chromatin are likely important adaptations for achieving a small cell size. %B Proceedings of the National Academy of Sciences of the United States of America %V 104 %P 7705–7710 %G eng %U http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=17460045 %0 Journal Article %J Aquatic Microbial Ecology %D 2006 %T Analysis of photosynthetic picoeukaryote diversity at open ocean sites in the Arabian Sea using a PCR biased towards marine algal plastids %A Fuller, Nicholas J %A Campbell, Colin %A Allen, David J %A Pitt, Frances D %A Le Gall, F %A Vaulot, Daniel %A Scanlan, David J %K 2006 %K PICOCEAN %K PICODIV %K rcc %K SBR$_\textrmP$hyto$_\textrmD$PO %K sbr?hyto$_\textrmd$ipo %B Aquatic Microbial Ecology %V 43 %P 79–93 %G eng %R 10.3354/ame043079 %0 Journal Article %J Proceedings of the National Academy of Sciences of the United States of America %D 2006 %T Genome analysis of the smallest free-living eukaryote Ostreococcus tauri unveils many unique features %A Derelle, Evelyne %A Ferraz, Conchita %A Rombauts, Stephane %A Rouze, Pierre %A Worden, Alexandra Z %A Robbens, Steven %A Partensky, Frédéric %A Degroeve, Sven %A Echeynie, Sophie %A Cooke, Richard %A Saeys, Yvan %A Wuyts, Jan %A Jabbari, Kamel %A Bowler, Chris %A Panaud, Olivier %A Piegu, Benoit %A Ball, Steven G %A Ral, Jean-Philippe %A Bouget, François-Yves %A Piganeau, Gwenael %A De Baets, Bernard %A Picard, André %A Delseny, Michel %A Demaille, Jacques %A Van de Peer, Yves %A Moreau, Hervé %K rcc %K RCC745 %K SBR$_\textrmP$hyto %X The green lineage is reportedly 1,500 million years old, evolving shortly after the endosymbiosis event that gave rise to early photosynthetic eukaryotes. In this study, we unveil the complete genome sequence of an ancient member of this lineage, the unicellular green alga Ostreococcus tauri (Prasinophyceae). This cosmopolitan marine primary producer is the world's smallest free-living eukaryote known to date. Features likely reflecting optimization of environmentally relevant pathways, including resource acquisition, unusual photosynthesis apparatus, and genes potentially involved in C4 photosynthesis, were observed, as was downsizing of many gene families. Overall, the 12.56-Mb nuclear genome has an extremely high gene density, in part because of extensive reduction of intergenic regions and other forms of compaction such as gene fusion. However, the genome is structurally complex. It exhibits previously unobserved levels of heterogeneity for a eukaryote. Two chromosomes differ structurally from the other eighteen. Both have a significantly biased G+C content, and, remarkably, they contain the majority of transposable elements. Many chromosome 2 genes also have unique codon usage and splicing, but phylogenetic analysis and composition do not support alien gene origin. In contrast, most chromosome 19 genes show no similarity to green lineage genes and a large number of them are specialized in cell surface processes. Taken together, the complete genome sequence, unusual features, and downsized gene families, make O. tauri an ideal model system for research on eukaryotic genome evolution, including chromosome specialization and green lineage ancestry. %B Proceedings of the National Academy of Sciences of the United States of America %V 103 %P 11647–11652 %G eng %U http://www.pnas.org/cgi/content/abstract/103/31/11647 %R 10.1073/pnas.0604795103 %0 Journal Article %J Environmental Microbiology %D 2005 %T Ecotype diversity in the marine picoeukaryote Ostreococcus (Chlorophyta, Prasinophyceae). %A Rodriguez, F %A Derelle, E %A Guillou, L %A Le Gall, F %A Vaulot, D %A Moreau, H %K rcc %K RCC113 %K Rcc141 %K RCC143 %K RCC343 %K RCC356 %K RCC371 %K RCC393 %K rcc410 %K RCC420 %K RCC434 %K rcc501 %K RCC658 %K RCC745 %K SBR$_\textrmP$hyto$_\textrmD$PO %B Environmental Microbiology %V 7 %P 853–859 %G eng %R 10.1111/j.1462-2920.2005.00758.x %0 Journal Article %J FEMS Microbiology Ecology %D 2005 %T Mapping of picoeucaryotes in marine ecosystems with quantitative PCR of the 18S rRNA gene %A Zhu, Fei %A Massana, Ramon %A Not, Fabrice %A Marie, Dominique %A Vaulot, Daniel %K Coastal ecosystems %K Ecology %K Fluorescent in situ hybridization %K Micromonas %K picoplankton %K prasinophytes %K Quantitative PCR %K rcc %X A quantitative PCR (QPCR) assay based on the use of SYBR Green I was developed to assess the abundance of specific groups of picoeukaryotes in marine waters. Six primer sets were designed targeting four different taxonomic levels: domain (Eukaryota), division (Chlorophyta), order (Mamiellales) and genus (Bathycoccus, Micromonas, and Ostreococcus). Reaction conditions were optimized for each primer set which was validated in silico, on agarose gels, and by QPCR against a variety of target and non-target cultures. The approach was tested by estimating gene copy numbers for Micromonas, Bathycoccus, and Ostreococcus in seawater samples to which cultured cells were added in various concentrations. QPCR was then used to determine that rRNA gene (rDNA) copy number varied from one to more than 12,000 in 18 strains of phytoplankton. Finally, QPCR was applied to environmental samples from a Mediterranean Sea coastal site and the results were compared to those obtained by Fluorescent in situ hybridization (FISH). The data obtained demonstrate that Chlorophyta and more specifically Mamiellales were important in these waters, especially during the winter picoplankton bloom. The timing of major abundance peaks of the targeted species was similar by QPCR and FISH. When used in conjunction with other techniques such as FISH or gene clone libraries, QPCR appears as very promising to quickly obtain data on the ecological distribution of important phytoplankton groups. Data interpretation must take into account primer specificity and the varying rRNA gene copy number among eukaryotes. ?? 2004 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved. %B FEMS Microbiology Ecology %V 52 %P 79–92 %G eng %0 Book Section %B Algal culturing techniques %D 2005 %T Phytoplankton cell counting by flow cytometry %A Marie, D %A Simon, N %A Vaulot, D %E Andersen, R A %K 2005 %K PICODIV %K rcc %K SBR$_\textrmP$hyto$_\textrmD$PO %K sbr?hyto %B Algal culturing techniques %I Academic Press %P 253–267 %G eng %0 Journal Article %D 2004 %T Composition and temporal variability of picoeukaryote communities at a coastal site of the English Channel from 18S rDNA sequences %A Romari, Khadidja %A Vaulot, Daniel %K Micromonas %K rcc %X Abstract We analyzed picoeukaryote assemblages at a French coastal site of the English Channel by sequencing cloned eukaryotic 18S rRNA genes in eight genetic libraries constructed from environmental samples (seven coastal , one estuarine) collected at different periods of the ... %V 49 %P 784–798 %G eng %R 10.4319/lo.2004.49.3.0784 %0 Journal Article %J Protist %D 2004 %T Diversity of picoplanktonic prasinophytes assessed by direct nuclear SSU rDNA sequencing of environmental samples and novel isolates retrieved from oceanic and coastal marine ecosystems %A Guillou, Laure %A Eikrem, W %A Chrétiennot-Dinet, M.-J. %A Le Gall, F %A Massana, R %A Romari, K %A Pedrós-Alió, C %A Vaulot, D %K 2004 %K PICODIV %K rcc %K SBR$_\textrmP$hyto$_\textrmD$PO %K sbr?hyto %K SOMLIT %B Protist %V 155 %P 193–214 %G eng %R 10.1078/143446104774199592 %0 Journal Article %J Nova Hedwigia %D 2004 %T The roscoff culture collection (RCC): a collection dedicated to marine picoplankton %A Vaulot, D %A Le Gall, F %A Marie, D %A Guillou, L %A Partensky, F %K 10$_\textrmb$est %K 2004 %K PICODIV %K rcc %K SBR$_\textrmP$hyto$_\textrmD$PO %K sbr?hyto %B Nova Hedwigia %V 79 %P 49–70 %G eng %R 10.1127/0029-5035/2004/0079-0049 %0 Journal Article %J Applied and Environmental Microbiology %D 2003 %T Clade-specific 16S ribosomal DNA oligonucleotides reveal the predominance of a single marine Synechococcus clade throughout a stratified water column in the Red Sea %A Fuller, Nicholas J %A Marie, Dominique %A Partensky, Frédéric %A Vaulot, Daniel %A Post, Anton F %A Scanlan, David J %K 2003 %K PICODIV %K rcc %K SBR$_\textrmP$hyto %K sbr?hyto %X Phylogenetic relationships among members of the marine Synechococcus genus were determined following sequencing of the 16S ribosomal DNA (rDNA) from 31 novel cultured isolates from the Red Sea and several other oceanic environments. This revealed a large genetic diversity within the marine Synechococcus cluster consistent with earlier work but also identified three novel clades not previously recognized. Phylogenetic analyses showed one clade, containing halotolerant isolates lacking phycoerythrin (PE) and including strains capable, or not, of utilizing nitrate as the sole N source, which clustered within the MC-A (Synechococcus subcluster 5.1) lineage. Two copies of the 16S rRNA gene are present in marine Synechococcus genomes, and cloning and sequencing of these copies from Synechococcus sp. strain WH 7803 and genomic information from Synechococcus sp. strain WH 8102 reveal these to be identical. Based on the 16S rDNA sequence information, clade-specific oligonucleotides for the marine Synechococcus genus were designed and their specificity was optimized. Using dot blot hybridization technology, these probes were used to determine the in situ community structure of marine Synechococcus populations in the Red Sea at the time of a Synechococcus maximum during April 1999. A predominance of genotypes representative of a single clade was found, and these genotypes were common among strains isolated into culture. Conversely, strains lacking PE, which were also relatively easily isolated into culture, represented only a minor component of the Synechococcus population. Genotypes corresponding to well-studied laboratory strains also appeared to be poorly represented in this stratified water column in the Red Sea. %B Applied and Environmental Microbiology %V 69 %P 2430–2443 %G eng %U http://aem.asm.org/cgi/content/abstract/69/5/2430 %R 10.1128/AEM.69.5.2430-2443.2003 %0 Journal Article %J Applied and Environmental Microbiology %D 2003 %T Quantitative assessment of picoeucaryotes in the natural environment using taxon specific oligonucleotide probes in association with TSA-FISH (Tyramide Signal Amplification - Fluorescent In Situ Hybridization) and flow cytometry %A Biegala, I C %A Not, F %A Vaulot, D %A Simon, N %K 2003 %K PICODIV %K rcc %K SBR$_\textrmP$hyto %K sbr?hyto %K SOMLIT %B Applied and Environmental Microbiology %V 69 %P 5519–5529 %G eng %R 10.1128/AEM.69.9.5519-5529.2003 %0 Journal Article %D 2002 %T Application of fluorescent in situ hybridization coupled with tyramide signal amplification (FISH-TSA) to assess eukaryotic picoplankton composition %A Not, F %A Simon, N %A Biegala, IC %A Vaulot, D %K rcc %X Photosynthetic picoeukaryotes (phytoplankton cells with a diameter smaller than 2 to 3 ??m) contribute significantly to both biomass and primary production in the oligotrophic open ocean and coastal waters, at certain times of the year. The identification of these organisms is difficult because of their small size and simple morphology, therefore hindering detailed ecological studies of their distribution and role. In this paper, we demonstrate the use of oligonucleotide probes specific to algal classes or to lower order taxa in combination with fluorescent in situ hybridization and tyramide signal amplification (FISH-TSA) to determine eukaryotic picophytoplankton diversity. Target cells were detected and enumerated using epifluorescence microscopy. The sensitivity of the technique and the specificity of the probes were tested on pure and mixed picoplanktonic strains, as well as on natural samples from the English Channel. In these samples, the community was dominated by cells belonging to the division Chlorophyta. Haptophyta, Bolidophyceae and Pelagophyceae were also detected at low abundance. The FISH-TSA method is readily applicable to the study of picoplankton diversity in natural communities. %V 28 %P 157–166 %G eng %R 10.3354/ame028157 %0 Journal Article %J Applied and Environmental Microbiology %D 2001 %T Cell cycle regulation by light in Prochlorococcus strains %A Jacquet, S %A Partensky, F %A Marie, D %A Casotti, R %A Vaulot, D %K cyanobacteria %K Equatorial Pacific %K Gene Expression %K Growth %K Mediterranean Sea %K North Atlantic %K Photosynthetic Prokaryote %K picoplankton %K Populations %K rcc %K Synechococcus %X

The effect of light on the synchronization of cell cycling was investigated in several strains of the oceanic photosynthetic prokaryote Prochlorococcus using flow cytometry. When exposed to a light-dark (L-D) cycle with an irradiance of 25 mu mol of quanta m(-2) s(-1), the low-light-adapted strain SS 120 appeared to be better synchronized than the high-light-adapted strain PCC 9511. Submitting LD-entrained populations to shifts (advances or delays) in the timing of the "light on" signal translated to corresponding shifts in the initiation of the S phase, suggesting that this signal is a key parameter for the synchronization of population cell cycles. Cultures that were shifted from an L-D cycle to continuous irradiance showed persistent diel oscillations of flow-cytometric signals (light scatter and chlorophyll fluorescence) but with significantly reduced amplitudes and a phase shift. Complete darkness arrested most of the cells in the G(1), phase of the cell cycle, indicating that light is required to trigger the initiation of DNA replication and cell division. However, some cells also arrested in the S phase, suggesting that cell cycle controls in Prochlorococcus spp. are not as strict as in marine Synechococcus spp. Shifting Prochlorococcus cells from low to high irradiance translated quasi-instantaneously into an increase of cells in both the S and G(2) phases of the cell cycle and then into faster growth, whereas the inverse shift induced rapid slowing of the population growth rate. These data suggest a close coupling between irradiance levels and cell cycling in Prochloroeoccus spp.

%B Applied and Environmental Microbiology %V 67 %P 782–790 %G eng %R 10.1128/AEM.67.2.782-790.2001 %0 Journal Article %J Journal of Phycology %D 2001 %T Diel patterns of growth and division in marine picoplankton in culture %A Jacquet, S %A Partensky, F %A Lennon, J F %A Vaulot, D %K 2001 %K Cell Division %K Cyanobacteria Synechococcus %K Dividing Cells %K Equatorial Pacific %K flow cytometry %K Mediterranean Sea %K Natural Populations %K North Pacific Ocean %K Photosynthetic Picoplankton %K Picophytoplankton Dynamics %K rcc %K SBR$_\textrmP$hyto %K sbr?hyto %X {The effect of a 12:12-h light:dark (LD) cycle on the phasing of several cell parameters was explored in a variety of marine picophytoplanktonic strains. These included the photosynthetic prokaryotes Pro-chlorococcus (strains MED 4, PCC 9511, and SS 120) and Synechococcus (strains ALMO 03, ROS 04, WH 7803, and WH 8103) and five picoeukaryotes (Bathycoccus prasinos Eikrem et Throndsen, Bolidomonas pacifica Guillou et Chretiennot-Dinet, Micromonas pusilla Manton et Parke, Pelagomonas calceolata Andersen et Saunders, and Pycnococcus provasolii Guillard et al.). Flow cytometric analysis was used to determine the relationship between cell light scatter, pigment fluorescence, DNA (when possible), and the LD cycle in these organisms. Asexpected, growth and division were tightly coupled to the LD cycle for all of these strains. For both Prochlorococcus and picoeukaryotes, chi and intracellular carbon increased throughout the light period as estimated by chi fluorescence and light scatter, respectively. In response to cell division, these parameters decreased regularly during the early part of the dark period, a decrease that either continued throughout the dark period or stopped for the second half of the dark period. For Synechococcus, the decrease of chi and scatter occurred earlier (in the middle of the light period), and for some strains these cellular parameters remained constant throughout the dark period. The timing of division was very similar for all picoeukaryotes and occurred just before the subjective dusk, whereas it was more variable between the different Prochlorococcus and Synechococcus strains. The burst of division for Prochlorococcus SS 120 and PCC 9511 was recorded at the subjective dusk, whereas the MED 4 strain divided later at night. Synechococcus ALMO 03, ROS 04, and WH 7803, which have a low phycourobilin to phycoerythrobilin (PUB:PEB) ratio, divided earlier, and their division was restricted to the light period. In contrast, the high PUB:PEB Synechococcus strain WH 8103 divided preferentially at night. There was a weak linear relationship between the FALS(max):FALS(min) ratio and growth rate calculated from cell counts (r = 0.83 %B Journal of Phycology %V 37 %P 357–369 %G eng %R 10.1046/j.1529-8817.2001.037003357.x %0 Journal Article %J Aquatic Microbial Ecology %D 2001 %T Grazing impact of two small heterotrophic flagellates on Prochlorococcus and Synechococcus %A Guillou, L %A Jacquet, S %A Chrétiennot-Dinet, M.-J. %A Vaulot, D %K 2001 %K Algal Class %K Equatorial Pacific %K Growth Rates %K Laboratory Cultures %K Marine %K Nanoplankton %K PICODIV %K picoplankton %K Prey %K rcc %K SBR$_\textrmP$hyto %K sbr?hyto %K Size %K Sp Nov %X In open oceanic waters, phytoplankton biomass is dominated by organisms below 2 to 3 mum in size (pico- and small nanophytoplankton). The cell concentration of these populations is very stable in time and space as a consequence of nutrient limitation and strong grazing pressure, Although the identity of the organisms that directly graze on picoplankton is largely unknown, they are thought to be very small, i.e. ¡3 to 5 ¡mu¿m, Here, we analyze the grazing impact of 2 small flagellates, Symbiomonas scintillans and Picophagus flagellatus, upon 2 oceanic cyanobacteria, Prochlorococcus and Synechococcus. S. scintillans does not feed on the 2 cyanobacteria. In contrast, P. flagellatus appears as an active predator capable of drastically reducing prey concentrations. The flagellate displays a substantial division rate of the order of 2 doublings d(-1) when fed on Prochlorococcus cells, but no significant growth is recorded when Synechococcus is used as prey. As the majority (¿ 80%) of P. flagellatus cells can pass throughout a 2 mum filter, the impact of such tiny predators should be taken into consideration during field experiments that rely on size fractionation to separate grazers from prey. %B Aquatic Microbial Ecology %V 26 %P 201–207 %G eng %R 10.3354/ame026201 %0 Journal Article %J Marine Ecology - Progress Series %D 2000 %T Feeding rate of the oyster Crassostrea gigas in a natural planktonic community of the Mediterranean Thau Lagoon %A Dupuy, C %A Vaquer, A %A LamHoai, T %A Rougier, C %A Mazouni, N %A Lautier, J %A Collos, Y %A LeGall, S %K ABUNDANCE %K bivalve %K carbon %K COASTAL WATERS %K EPIFLUORESCENCE MICROSCOPY %K FILTRATION-RATE %K food source %K FOOD-CHAINS %K GEUKENSIA-DEMISSA %K heterotrophic protist %K microbial food web %K MYTILUS-EDULIS %K oyster %K PARTICLE SELECTION %K picophytoplankton %K rcc %K RETENTION %K Thau Lagoon %K trophic link %X The Mediterranean Thau Lagoon is an important oyster farming area in Europe. Oyster growth rates are among the highest in France, although chlorophyll a concentration is low. Previous studies have demonstrated that picophytoplankton, nano-microphytoplankton, dinoflagellates and loricate ciliates such as tintinnids are abundant. However, heterotrophic flagellates and aloricate ciliates have not been investigated. The aim of this study was to assess picophytoplankton, protist and zooplankton abundances in the Lagoon and to investigate the particular structure of the microbial food web, which may explain such paradoxical oyster growth. In oligotrophic waters in the Thau Lagoon, the picoeukaryote Ostreococcus tauri is the dominant autotrophic picoplankter, with an abundance maximum in summer. On 17 August 1998, following a rainfall event, pico- and nanophytoplankton abundances were not as high as expected and we observed a high abundance of large diatoms. At this time, the available carbon resources were produced by microphytoplankton (84.5%), and picoplank-tonic cells represented only 1.27 % in terms of carbon. Heterotrophic cells were low in abundance and constituted ¡14% of carbon resources. In order to evaluate the importance of the 'protozoan trophic link' for energy transfer from the microbial food web to large benthic suspension feeders, the oyster Crassostrea gigas was offered a planktonic community as potential prey. In the grazing experiment, all ¿5 mum flagellates, microphytoplankton, dinoflagellates, ciliates and large zooplankton were retained by the oyster gills. Only flagellates ¡5 pm and O. Tauri were not very well retained (45 and 2% respectively). The high clearance rates of C. Gigas found in this experiment can be explained by a low concentration of suspended particulate matter (0.65 mg l(-1)). The oysters adapted their retention mechanism when they Lived in oligotrophic waters. These results indicate that, under the given experimental conditions, picophytoplankton did not represent a valuable trophic resource for farmed oysters because (1) C. Gigas cannot retain picoparticles and (2) the picoplankton represented a poor carbon resource capable of being transferred via a weak heterotrophic protist community. In the oyster pens of the Thau Lagoon during this study, microphytoplanktonic primary producers, in particular diatoms, were the main food sources for bivalve suspension feeders. %B Marine Ecology - Progress Series %V 205 %P 171–184 %G eng %R 10.3354/meps205171 %0 Journal Article %J Journal of Phycology %D 1999 %T Bolidomonas: a new genus with two species belonging to a new algal class, the Bolidophyceae (Heterokonta) %A Guillou, L %A Chrétiennot-Dinet, M.-J. %A Medlin, L K %A Claustre, H %A Loiseaux-de Goër, S %A Vaulot, D %K 10$_\textrmb$est %K 1999 %K Bolidophyceae %K CELL-CYCLE %K CHRYSOPHYCEAE %K diatoms %K DIVINYL-CHLOROPHYLL %K FINE-STRUCTURE %K FLAGELLAR APPARATUS %K Heterokonta %K Marine %K marine picoeukaryotes %K oligotrophic ocean %K rcc %K RNA %K SBR$_\textrmP$hyto %K sbr?hyto %K SEQUENCE %K sp-nov %K stramenopiles %K ultrastructure %X A new algal class, the Bolidophyceae (Heterokonta), is described from one genus, Bolidomonas, gen, nov., and two species, Bolidomonas pacifica, sp, nov and Bolidomonas mediterranea, sp, nov., isolated from the equatorial Pacific Ocean and the Mediterranean Sea, respectively. Both species are approximately 1.2 mu m in diameter and have two unequal flagella; the longer flagellum bears tubular hairs, whereas the shorter is smooth. The flagellar basal apparatus is restricted to two basal bodies, and there is no transitional helix. Cells are naked, devoid of walls or siliceous structures. The internal cellular organization is simple with a single plastid containing a ring genophore and a girdle lamella, one mitochondrion with tubular cristae, and one Golgi apparatus close to the basal bodies. The Mediterranean and the Pacific species differ in the insertion angle between their flagella and their pattern of swimming, these differences possibly being linked to each other. Analyses of the SSU rDNA gene place the two strains as a sister group to the diatoms, Moreover, pigment analyses confirm this position, as fucoxanthin is found as the major carotenoid in both lineages. These data strongly suggest that the ancestral heterokont that gave rise to the diatom lineage was probably a biflagellated unicell. %B Journal of Phycology %V 35 %P 368–381 %G eng %R 10.1046/j.1529-8817.1999.3520368.x %0 Journal Article %J Applied and Environmental Microbiology %D 1999 %T Diversity and abundance of Bolidophyceae (Heterokonta) in two oceanic regions %A Guillou, L %A Moon-van der Staay, S Y %A Claustre, H %A Partensky, F %A Vaulot, D %K 1999 %K ATLANTIC %K BACTERIOPLANKTON %K community structure %K flow-cytometry %K MOLECULAR PHYLOGENY %K PACIFIC %K phytoplankton %K PIGMENT SIGNATURES %K rcc %K RNA GENE SEQUENCE %K SBR$_\textrmP$hyto %K sbr?hyto %K ULTRAPHYTOPLANKTON %X The diversity and abundance of the Bolidophyceae (Heterokonta), a newly described picoplanktonic algal class which is a sister group to the diatoms, was assessed in the equatorial Pacific Ocean and in the Mediterranean Sea by culture isolation, molecular biology techniques, and pigment analyses. Eight strains of Bolidophyceae were isolated in culture from different mesotrophic and oligotrophic areas. The corresponding small subunit (SSU) rRNA gene sequences allowed us to design two probes specific for the Bolidophyceae. These probes have been used in natural samples (i) to selectively amplify and detect Bolidophyceae sequences and (ii) to quantify the relative abundance of Bolidophyceae within the picoeukaryote community. Sequences available to date indicate that the class Bolidophyceae comprises at least three different clades, two corresponding to the previously described species Bolidomonas pacifica and Bolidomonas mediterranea and the third one corresponding to a subspecies of B. Pacifica. Amplification of the SSU rRNA gene from natural samples with universal primers and hybridization using a Bolidomonas-specific probe followed by a eukaryote-specific probe allowed us to estimate the contribution of the Bolidophyceae to the eukaryotic DNA in both Pacific and Mediterranean waters to be lower than 1%. Similarly, high-performance liquid chromatography analyses of fucoxanthin, the major carotenoid present in Bolidophyceae, indicated that less than 4% of the total chlorophyll a in the picoplanktonic fraction in the equatorial Pacific was due to Bolidophyceae. Consequently, although strains of Bolidophyceae have been isolated from samples collected at several stations, this new class seems to have been a minor component of the natural picoeukaryotic populations in the ecosystems investigated, at least during the periods sampled. %B Applied and Environmental Microbiology %V 65 %P 4528–4536 %G eng %R 10.1128/AEM.65.10.4528-4536.1999 %0 Journal Article %J Protist %D 1999 %T Symbiomonas scintillans gen. et sp nov and Picophagus flagellatus gen. et sp nov (Heterokonta): Two new heterotrophic flagellates of picoplanktonic size %A Guillou, L %A Chrétiennot-Dinet, M.-J. %A Boulben, S %A Moon-van der Staay, S Y %A Vaulot, D %K 1999 %K APPARATUS %K DEVELOPAYELLA-ELEGANS %K EMPHASIS %K MOLECULAR PHYLOGENY %K picophytoplankton %K PLASTIDS %K rcc %K RDNA %K SBR$_\textrmP$hyto %K sbr?hyto %K SEQUENCES %X Two new oceanic free-living heterotrophic Heterokonta species with picoplanktonic size (¡ 2 mu m) are described, Symbiomonas scintillans Guillou et Chretiennot-Dinet gen. Ef sp. Nov, was isolated from samples collected both in the equatorial Pacific Ocean and the Mediterranean Sea. This new species possesses ultrastructural features of the bicosoecids, such as the absence of a helix in the flagellar transitional region (found in Cafeteria roenbergensis and in a few bicosoecids), and a flagellar root system very similar to that of C. Roenbergensis, Acronema sippewissettensis, and Bicosoeca maris. This new species is characterized by a single flagellum with mastigonemes, the presence of endosymbiotic bacteria located close to the nucleus, the absence of a lorica and a R3 root composed of a 6+3+x microtubular structure. Phylogenetical analyses of nuclear-encoded SSU rDNA gene sequences indicate that this species is close to the bicosoecids C. Roenbergensis and Siluania monomastiga. Picophagus flagellatus Guillou et Chretiennot-Dinet gen. Et sp. Nov. Was collected in the equatorial Pacific Ocean, Cells are naked and possess two flagella, This species is characterized by the lack of a transitional helix and lateral filaments on the flagellar tubular hairs, the absence of siliceous scales, two unequal flagella, R1 + R3 roots, and the absence of a rhizoplast. SSU rDNA analyses place this strain at the base of the Chrysophyceae/Synurophyceae lineages. %B Protist %V 150 %P 383–398 %G eng %R 10.1016/S1434-4610(99)70040-4 %0 Journal Article %J European Journal of Phycology %D 1996 %T High degree of genetic variation in Prochlorococcus (Prochlorophyta) revealed by RFLP analysis %A Scanlan, D J %A Hess, W R %A Partensky, F %A Newman, J %A Vaulot, D %K DIVINYL CHLOROPHYLL-A %K FAMILY %K Marine Synechococcus %K Mediterranean Sea %K Multiple Evolutionary Origins %K north-atlantic %K NUCLEOTIDE-SEQUENCE %K picoplankton %K Prokaryote %K rcc %K RCC SBR$_\textrmP$hyto %K UNICELLULAR CYANOBACTERIUM %B European Journal of Phycology %V 31 %P 1–9 %G eng %R 10.1080/09670269600651131 %0 Journal Article %J Phycologia %D 1995 %T A new marine picoeucaryote: Ostreococcus tauri gen. et sp. nov. (Chlorophyta, Prasinophyceae) %A Chrétiennot-Dinet, M.-J. %A Courties, C %A Vaquer, A %A Neveux, J %A Claustre, H %A Lautier, J %A Machado, M C %K FRESH-WATER ECOSYSTEMS %K morphology %K picoplankton %K pigments %K PROCHLOROCOCCUS-MARINUS %K Prokaryote %K rcc %K RCC745 %K Size %B Phycologia %V 34 %P 285–292 %G eng %R 10.2216/i0031-8884-34-4-285.1 %0 Journal Article %J Journal of Phycology %D 1994 %T Characterization of oceanic photosynthetic picoeukaryotes by flow cytometry analysis %A Simon, N %A Barlow, R G %A Marie, D %A Partensky, F %A Vaulot, D %K flow cytometry %K hplc %K pigments %K rcc %K RCC SBR$_\textrmP$hyto %K \#PICOPLANKTON %B Journal of Phycology %V 30 %P 922–935 %G eng %R 10.1111/j.0022-3646.1994.00922.x %0 Journal Article %J Journal of Phycology %D 1994 %T Phaeocystis spp.: morphology, ploidy, pigment composition and genome size of cultured strains %A Vaulot, D %A Birrien, J.-L. %A Marie, D %A Casotti, R %A Veldhuis, M J W %A Kraay, G W %A Chrétiennot-Dinet, M.-J. %K rcc %K RCC SBR$_\textrmP$hyto %B Journal of Phycology %V 30 %P 1022–1035 %G eng %R 10.1111/j.0022-3646.1994.01022.x %0 Journal Article %J Plant Physiology %D 1993 %T Photoacclimation of Prochlorococcus sp. (Prochlorophyta) strains isolated from the North Atlantic and the Mediterranean Sea %A Partensky, F %A Hoepffner, N %A Li, W K W %A Ulloa, O %A Vaulot, D %K hplc %K Photosynthesis %K Pigment %K rcc %K RCC SBR$_\textrmP$hyto %K sbr?hyto %K \#PROCHLOROPHYTE %B Plant Physiology %V 101 %P 295–296 %G eng %R 10.1104/pp.101.1.285 %0 Journal Article %J Journal of Marine Research %D 1993 %T Prochlorococcus and Synechococcus: a comparative study of their size, pigmentation and related optical properties %A Morel, A %A Ahn, Y.-W. %A Partensky, F %A Vaulot, Daniel %A Claustre, H %K 1993 %K hplc %K OPTICS %K Pigment %K rcc %K SBR$_\textrmP$hyto %K sbr?hyto %K Synechococcus %K \#PROCHLOROPHYTE %B Journal of Marine Research %V 51 %P 617–649 %G eng %R 10.1357/0022240933223963 %0 Book Section %B Photosynthetic picoplankton %D 1986 %T Biological and ecological characterization of the marine unicellular cyanobacterium Synechococcus %A Waterbury, J B %A Watson, S W %A Valois, F W %A Franks, D G %E Platt, T %E Li, W K W %K Canad. Bull. Fish. Aquatic Sci. %K phytoplankton %K rcc %K Synechococcus %B Photosynthetic picoplankton %V 214 %P 71–120 %G eng