%0 Journal Article %J Environmental Microbiology %D 2023 %T The Bay of Bengal exposes abundant photosynthetic picoplankton and newfound diversity along salinity-driven gradients %A Strauss, Jan %A Choi, Chang Jae %A Grone, Jonathan %A Wittmers, Fabian %A Jimenez, Valeria %A Makareviciute-Fichtner, Kriste %A Bachy, Charles %A Jaeger, Gualtiero Spiro %A Poirier, Camille %A Eckmann, Charlotte %A Spezzano, Rachele %A Löscher, Carolin R. %A Sarma, V. V. S. S. %A Mahadevan, Amala %A Worden, Alexandra Z. %K RCC393 %K RCC809 %X The Bay of Bengal (BoB) is a 2,600,000 km2 expanse in the Indian Ocean upon which many humans rely. However, the primary producers underpinning food chains here remain poorly characterized. We examined phytoplankton abundance and diversity along strong BoB latitudinal and vertical salinity gradients-which have low temperature variation (27-29°C) between the surface and subsurface chlorophyll maximum (SCM). In surface waters, Prochlorococcus averaged 11.7 ± 4.4 × 104  cells ml-1 , predominantly HLII, whereas LLII and 'rare' ecotypes, HLVI and LLVII, dominated in the SCM. Synechococcus averaged 8.4 ± 2.3 × 104  cells ml-1 in the surface, declined rapidly with depth, and population structure of dominant Clade II differed between surface and SCM; Clade X was notable at both depths. Across all sites, Ostreococcus Clade OII dominated SCM eukaryotes whereas communities differentiated strongly moving from Arabian Sea-influenced high salinity (southerly; prasinophytes) to freshwater-influenced low salinity (northerly; stramenopiles, specifically, diatoms, pelagophytes, and dictyochophytes, plus the prasinophyte Micromonas) surface waters. Eukaryotic phytoplankton peaked in the south (1.9 × 104  cells ml-1 , surface) where a novel Ostreococcus was revealed, named here Ostreococcus bengalensis. We expose dominance of a single picoeukaryote and hitherto 'rare' picocyanobacteria at depth in this complex ecosystem where studies suggest picoplankton are replacing larger phytoplankton due to climate change. %B Environmental Microbiology %G eng %R 10.1111/1462-2920.16431 %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 Generic %D 2023 %T Coccolithophorids precipitate carbonate in clumped isotope equilibrium with seawater %A Clark, Alexander J. %A Torres-Romero, Ismael %A Jaggi, Madalina %A Bernasconi, Stefano M. %A Stoll, Heather M. %K RCC1130 %K RCC1303 %K RCC3370 %X Numerous recent studies have tested the clumped isotope (Δ47) thermometer on a variety of biogenic carbonates such as foraminifera and bivalves and showed that all follow a common calibration. While the sample size requirements for a reliable Δ47 measurement have decreased over the years, the availability and preservation of many biogenic carbonates is still 10 limited and/or require substantial time to be extracted from sediments in sufficient amounts. We thus determined the Δ47temperature relationship for coccolith carbonate, which is abundant and often well-preserved in sediments. The carbon and oxygen isotopic compositions of coccolith calcite have limited use in palaeoenvironmental reconstructions due to physiological effects that cause variability in the carbon and oxygen isotopic values. However, the relatively limited data available suggest that clumped isotopes may not be influenced by these effects. We cultured three species of coccolithophores in well15 constrained carbonate system conditions with a CO2(aq) between 5 and 45 μM and temperatures between 6°C and 27°C. %I EGUsphere %8 nov %G eng %U https://egusphere.copernicus.org/preprints/2023/egusphere-2023-2581/ %9 preprint %R 10.5194/egusphere-2023-2581 %0 Journal Article %J Algal Research %D 2023 %T Comparison of different small-scale cultivation methods towards the valorization of a marine benthic diatom strain for lipid production %A Arnaldo, Mary Dianne Grace %A Gamage, Nadeeshani Dehel %A Jaffrenou, Agathe %A Rabesaotra, Vony %A Mossion, Aurélie %A Wielgosz-Collin, Gaëtane %A Méléder, Vona %K RCC5813 %B Algal Research %P 103327 %G eng %U https://linkinghub.elsevier.com/retrieve/pii/S2211926423003600 %R 10.1016/j.algal.2023.103327 %0 Journal Article %J Frontiers in Ecology and Evolution %D 2022 %T Assessment of biodiversity, global distribution, and putative ecological niches of suessiacean dinoflagellates by DNA metabarcoding %A Jang, Se Hyeon %K RCC2013 %X Dinoflagellates in the family Suessiaceae, so-called suessiacean dinoflagellates, play diverse roles in aquatic ecosystems, being distributed from tropical to polar waters and from marine to freshwater habitats and encompassing free-living forms, symbionts, and parasites. Despite their importance due to the variety of ecological roles and biodiversity, very few studies have characterized small suessiacean species. Recent advances in molecular techniques could provide insights into the yet unexplored ecological roles they play in aquatic environments. Using a global DNA metabarcoding dataset, this study elucidated the hidden biodiversity, global distribution, and ecological characteristics of suessiacean dinoflagellates. The results of this study indicated that the family Suessiaceae was the sixth highest in terms of read count and the ninth highest in terms of amplicon sequence variant (ASV) richness from a total of 42 categorized dinoflagellate families, suggesting that their global abundance has been greatly underestimated. Furthermore, metabarcodes of suessiacean dinoflagellates were found to be cosmopolitan in distribution, although the ecological niche of each taxon was distinctly different within the group based on their latitudinal and vertical distribution patterns. Moreover, phylogenetic analysis discovered at least five new phylogenetic groups and three new individual species within the family. Collectively, the findings of this study highlight the significance of suessiacean dinoflagellates in global aquatic ecosystems and reveal the importance of big data obtained from environmental DNA in exploring the ecological functions of understudied species. %B Frontiers in Ecology and Evolution %V 10 %G eng %U https://www.frontiersin.org/articles/10.3389/fevo.2022.1010854 %R 10.3389/fevo.2022.1010854 %0 Journal Article %J Communications Biology %D 2022 %T Genomic adaptation of the picoeukaryote Pelagomonas calceolata to iron-poor oceans revealed by a chromosome-scale genome sequence %A Guérin, Nina %A Ciccarella, Marta %A Flamant, Elisa %A Frémont, Paul %A Mangenot, Sophie %A Istace, Benjamin %A Noel, Benjamin %A Belser, Caroline %A Bertrand, Laurie %A Labadie, Karine %A Cruaud, Corinne %A Romac, Sarah %A Bachy, Charles %A Gachenot, Martin %A Pelletier, Eric %A Alberti, Adriana %A Jaillon, Olivier %A Wincker, Patrick %A Aury, Jean-Marc %A Carradec, Quentin %K Biogeography %K comparative genomics %K metagenomics %K RCC100 %K Water microbiology %X The smallest phytoplankton species are key actors in oceans biogeochemical cycling and their abundance and distribution are affected with global environmental changes. Among them, algae of the Pelagophyceae class encompass coastal species causative of harmful algal blooms while others are cosmopolitan and abundant. The lack of genomic reference in this lineage is a main limitation to study its ecological importance. Here, we analysed Pelagomonas calceolata relative abundance, ecological niche and potential for the adaptation in all oceans using a complete chromosome-scale assembled genome sequence. Our results show that P. calceolata is one of the most abundant eukaryotic species in the oceans with a relative abundance favoured by high temperature, low-light and iron-poor conditions. Climate change projections based on its relative abundance suggest an extension of the P. calceolata habitat toward the poles at the end of this century. Finally, we observed a specific gene repertoire and expression level variations potentially explaining its ecological success in low-iron and low-nitrate environments. Collectively, these findings reveal the ecological importance of P. calceolata and lay the foundation for a global scale analysis of the adaptation and acclimation strategies of this small phytoplankton in a changing environment. Genomic inference reveals potential climate change-driven range expansion of the phytoplankton species Pelagomonas calceolata. %B Communications Biology %V 5 %P 1–14 %G eng %U https://www.nature.com/articles/s42003-022-03939-z %R 10.1038/s42003-022-03939-z %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 Microbiology Spectrum %D 2022 %T Marine \textit{Synechococcus sp. Strain WH7803 Shows Specific Adaptative Responses to Assimilate Nanomolar Concentrations of Nitrate %A Domínguez-Martín, Maria Agustina %A López-Lozano, Antonio %A Melero-Rubio, Yesica %A Gómez-Baena, Guadalupe %A Jiménez-Estrada, Juan Andrés %A Kukil, Kateryna %A Díez, Jesús %A García-Fernández, José Manuel %E Hom, Erik F. Y. %K rcc752 %X Marine Synechococcus, together with Prochlorococcus, contribute to a significant proportion of the primary production on Earth. The spatial distribution of these two groups of marine picocyanobacteria depends on different factors such as nutrient availability and temperature. Some Synechococcus ecotypes thrive in mesotrophic and moderately oligotrophic waters, where they exploit both oxidized and reduced forms of nitrogen. Here, we present a comprehensive study, which includes transcriptomic and proteomic analyses of the response of Synechococcus sp. strain WH7803 to nanomolar concentrations of nitrate, compared to micromolar ammonium or nitrogen starvation. We found that Synechococcus has a specific response to a nanomolar nitrate concentration that differs from the response shown under nitrogen starvation or the presence of standard concentrations of either ammonium or nitrate. This fact suggests that the particular response to the uptake of nanomolar concentrations of nitrate could be an evolutionary advantage for marine Synechococcus against Prochlorococcus in the natural environment. %B Microbiology Spectrum %V 10 %P e00187–22 %8 aug %G eng %U https://journals.asm.org/doi/10.1128/spectrum.00187-22 %R 10.1128/spectrum.00187-22 %0 Journal Article %J Limnology and Oceanography %D 2022 %T Nutritional response of a coccolithophore to changing pH and temperature %A Johnson, Roberta %A Langer, Gerald %A Rossi, Sergio %A Probert, Ian %A Mammone, Marta %A Ziveri, Patrizia %K RCC1832 %X Coccolithophores are a calcifying unicellular phytoplankton group that are at the base of the marine food web, and their lipid content provides a source of energy to consumers. Coccolithophores are vulnerable to ocean acidification and warming, therefore it is critical to establish the effects of climate change on these significant marine primary producers, and determine potential consequences that these changes can have on their consumers. Here, we quantified the impact of changes in pH and temperature on the nutritional condition (lipid content, particulate organic carbon/nitrogen), growth rate, and morphology of the most abundant living coccolithophore species, Emiliania huxleyi. We used a regression type approach with nine pH levels (ranging from 7.66 to 8.44) and two temperatures (15°C and 20°C). Lipid production was greater under reduced pH, and growth rates were distinctly lower at 15°C than at 20°C. The production potential of lipids, which estimates the availability of lipids to consumers, increased under 20°C, but decreased under low pH. The results indicate that, while consumers will benefit energetically under ocean warming, this benefit will be mitigated by ocean acidification. The carbon to nitrogen ratio was higher at 20°C and low pH, indicating that the nutritional quality of coccolithophores for consumers will decline under climate change. The impact of low pH on the structural integrity of the coccosphere may also mean that coccolithophores are easier to digest for consumers. Many responses suggest cellular stress, indicating that increases in temperature and reductions in pH may have a negative impact on the ecophysiology of coccolithophores. %B Limnology and Oceanography %V n/a %G eng %U http://onlinelibrary.wiley.com/doi/abs/10.1002/lno.12204 %R 10.1002/lno.12204 %0 Journal Article %J ALGAE %D 2021 %T Bioluminescence capability and intensity in the dinoflagellate Alexandrium species %A Park, Sang Ah %A Jeong, Hae Jin %A Ok, Jin %A Kang, Heechang %A You, Jihyun %A Eom, Se %A Yoo, Yeong %A Lee, Moo Joon %K RCC4104 %X Some species in the dinoflagellate genus Alexandrium are bioluminescent. Of the 33 formally described Alexandrium species, the bioluminescence capability of only nine species have been tested, and eight have been reported to be bioluminescent. The present study investigated the bioluminescence capability of seven Alexandrium species that had not been tested. Alexandrium mediterraneum, A. pohangense, and A. tamutum were bioluminescent, but A. andersonii, A. hiranoi, A. insuetum, and A. pseudogonyaulax were not. We also measured the bioluminescent intensity of A. affine, A. fraterculus, A. mediterraneum, A. ostenfeldii, A. pacificum, A. pohangense, A. tamarense, and A. tamutum. The mean 200-second-integrated bioluminescence intensity per cell ranged from 0.02 to 32.2 × 104 relative luminescence unit per cell (RLU cell-1), and the mean maximum bioluminescence intensity per cell per second (BLMax) ranged from 0.01 to 10.3 × 104 RLU cell-1 s-1. BLMax was significantly correlated with the maximum growth rates of Alexandrium species, except for A. tamarense. A phylogenetic tree based on large subunit ribosomal DNA (LSU rDNA), showed that the bioluminescent species A. affine, A. catenella, A. fraterculus, A. mediterraneum, A. pacificum, and A. tamarense formed a large clade. However, the toxicity or mixotrophic capability of these species was split. Thus, their bioluminescence capability in this clade was more consistent than their toxicity or mixotrophic capability. Phylogenetic trees based on LSU rDNA and the luciferase gene of Alexandrium were consistent except for A. pohangense. The results of the present study can provide a basis for understanding the interspecific diversity in bioluminescence of Alexandrium. %B ALGAE %V 36 %G eng %R 10.4490/algae.2021.36.12.6 %0 Journal Article %J ISME Communications %D 2021 %T Dinophyceae can use exudates as weapons against the parasite Amoebophrya sp. (Syndiniales) %A Long, Marc %A Marie, Dominique %A Szymczak, Jeremy %A Toullec, Jordan %A Bigeard, Estelle %A Sourisseau, Marc %A Le Gac, Mickaël %A Guillou, Laure %A Jauzein, Cécile %K microbial ecology %K Plant ecology %K rcc %K RCC1627 %K RCC4383 %K RCC4714 %K RCC749 %K Water microbiology %X Parasites in the genus Amoebophrya sp. infest dinoflagellate hosts in marine ecosystems and can be determining factors in the demise of blooms, including toxic red tides. These parasitic protists, however, rarely cause the total collapse of Dinophyceae blooms. Experimental addition of parasite-resistant Dinophyceae (Alexandrium minutum or Scrippsiella donghaienis) or exudates into a well-established host-parasite coculture (Scrippsiella acuminata-Amoebophrya sp.) mitigated parasite success and increased the survival of the sensitive host. This effect was mediated by waterborne molecules without the need for a physical contact. The strength of the parasite defenses varied between dinoflagellate species, and strains of A. minutum and was enhanced with increasing resistant host cell concentrations. The addition of resistant strains or exudates never prevented the parasite transmission entirely. Survival time of Amoebophrya sp. free-living stages (dinospores) decreased in presence of A. minutum but not of S. donghaienis. Parasite progeny drastically decreased with both species. Integrity of the dinospore membrane was altered by A. minutum, providing a first indication on the mode of action of anti-parasitic molecules. These results demonstrate that extracellular defenses can be an effective strategy against parasites that protects not only the resistant cells producing them, but also the surrounding community. %B ISME Communications %V 1 %P 1–10 %G eng %U http://www.nature.com/articles/s43705-021-00035-x %R 10.1038/s43705-021-00035-x %0 Generic %D 2021 %T Dinophyceae use exudates as weapons against the parasite Amoebophrya sp. (Syndiniales) %A Marc, Long %A Dominique, Marie %A Jeremy, Szymczak %A Jordan, Toullec %A Estelle, Bigeard %A Marc, Sourisseau %A Mickael, Le Gac %A Laure, Guillou %A Cécile, Jauzein %K rcc %K RCC1627 %K RCC4383 %K RCC4714 %K RCC749 %X Parasites of the genus Amoebophrya sp. are important contributors to marine ecosystems and can be determining factors in the demise of blooms of Dinophyceae, including microalgae commonly responsible for toxic red tides. Yet they rarely lead to the total collapse of Dinophyceae blooms. The addition of resistant Dinophyceae (Alexandrium minutum or Scrippsiella donghaienis) or their exudate into a well-established host-parasite culture (Scrippsiella acuminata-Amoebophrya sp.) mitigated the success of the parasite and increased the survival of the sensitive host. Effect were mediated via water-borne molecules without the need of a physical contact. Severity of the anti-parasitic defenses fluctuated depending on the species, the strain and its concentration, but never totally prevented the parasite transmission. The survival time of Amoebophrya sp. free-living stages (dinospores) decreased in presence of A. minutum but not of S. donghaienis. The progeny drastically decreased with both species. Integrity of the membrane of dinospores was altered by A. minutum which provided a first indication on the mode of action of these anti-parasitic molecules. These results demonstrate that extracellular defenses are an effective strategy against parasites that does not only protect the resistant cells but also have the potential to affect the whole surrounding community. %P 2021.01.05.425281 %8 jan %G eng %U https://www.biorxiv.org/content/10.1101/2021.01.05.425281v1 %R 10.1101/2021.01.05.425281 %0 Book Section %B Progress in the Chemistry of Organic Natural Products 116 %D 2021 %T Marine Biodiscovery in a Changing World %A Reddy, Maggie M. %A Jennings, Laurence %A Thomas, Olivier P. %E Kinghorn, A. Douglas %E Falk, Heinz %E Gibbons, Simon %E Asakawa, Yoshinori %E Liu, Ji-Kai %E Dirsch, Verena M. %K Bioprospecting %K Biorepositories %K Data management system %K Marine biodiscovery %K Marine natural products %K Screenings %K taxonomy %X The term “marine biodiscovery” has been recently been adopted to describe the area of marine natural products dedicated to the search of new drugs. Several maritime countries such as Australia, New Zealand, South Korea, and Japan as well as some European countries have invested significantly in this area of research over the last 50 years. In the late 2000s, research in this field has received significant interest and support in Ireland for exploring new marine bioresources from the nutrient-rich waters of the Northeastern Atlantic Ocean. Despite undeniable success exemplified by the marketing of new drugs, especially in oncology, the integration of new technical but also environmental aspects should be considered. Indeed, global change, particularly in our oceans, such as climate change, biodiversity loss, and the emergence of microbial pathogens, not only affects the environment but ultimately contributes to social inequalities. In this contribution, new avenues and best practices are proposed, such as the development of biorepositories and shared data for the future of marine biodiscovery research. The extension of this type of scientific work will allow humanity to finally make the optimum use of marine bioresources. %B Progress in the Chemistry of Organic Natural Products 116 %S Progress in the Chemistry of Organic Natural Products %I Springer International Publishing %C Cham %P 1–36 %@ 978-3-030-80560-9 %G eng %U https://doi.org/10.1007/978-3-030-80560-9_1 %R 10.1007/978-3-030-80560-9_1 %0 Journal Article %J Proceedings of the National Academy of Sciences %D 2021 %T Molecular bases of an alternative dual-enzyme system for light color acclimation of marine \textit{Synechococcus cyanobacteria %A Grébert, Théophile %A Nguyen, Adam A. %A Pokhrel, Suman %A Joseph, Kes Lynn %A Ratin, Morgane %A Dufour, Louison %A Chen, Bo %A Haney, Allissa M. %A Karty, Jonathan A. %A Trinidad, Jonathan C. %A Garczarek, Laurence %A Schluchter, Wendy M. %A Kehoe, David M. %A Partensky, Frédéric %K RCC2374 %K to add %X

Marine Synechococcus cyanobacteria owe their ubiquity in part to the wide pigment diversity of their light-harvesting complexes. In open ocean waters, cells predominantly possess sophisticated antennae with rods composed of phycocyanin and two types of phycoerythrins (PEI and PEII). Some strains are specialized for harvesting either green or blue light, while others can dynamically modify their light absorption spectrum to match the dominant ambient color. This process, called type IV chromatic acclimation (CA4), has been linked to the presence of a small genomic island occurring in two configurations (CA4-A and CA4-B). While the CA4-A process has been partially characterized, the CA4-B process has remained an enigma. Here we characterize the function of two members of the phycobilin lyase E/F clan, MpeW and MpeQ, in Synechococcus sp. strain A15-62 and demonstrate their critical role in CA4-B. While MpeW, encoded in the CA4-B island and up-regulated in green light, attaches the green light-absorbing chromophore phycoerythrobilin to cysteine-83 of the PEII α-subunit in green light, MpeQ binds phycoerythrobilin and isomerizes it into the blue light-absorbing phycourobilin at the same site in blue light, reversing the relationship of MpeZ and MpeY in the CA4-A strain RS9916. Our data thus reveal key molecular differences between the two types of chromatic acclimaters, both highly abundant but occupying distinct complementary ecological niches in the ocean. They also support an evolutionary scenario whereby CA4-B island acquisition allowed former blue light specialists to become chromatic acclimaters, while former green light specialists would have acquired this capacity by gaining a CA4-A island.

%B Proceedings of the National Academy of Sciences %V 118 %P e2019715118 %G eng %U http://www.pnas.org/lookup/doi/10.1073/pnas.2019715118 %R 10.1073/pnas.2019715118 %0 Journal Article %J Nature Communications %D 2021 %T Morphological bases of phytoplankton energy management and physiological responses unveiled by 3D subcellular imaging %A Uwizeye, Clarisse %A Decelle, Johan %A Jouneau, Pierre-Henri %A Flori, Serena %A Gallet, Benoit %A Keck, Jean-baptiste %A Bo, Davide Dal %A Moriscot, Christine %A Seydoux, Claire %A Chevalier, Fabien %A Schieber, Nicole L. %A Templin, Rachel %A Allorent, Guillaume %A Courtois, Florence %A Curien, Gilles %A Schwab, Yannick %A Schoehn, Guy %A Zeeman, Samuel C. %A Falconet, Denis %A Finazzi, Giovanni %K RCC100 %K RCC4014 %K RCC827 %K RCC909 %X Phytoplankton account for a large proportion of global primary production and comprise a number of phylogenetically distinct lineages. Here, Uwizeye et al. use FIB-SEM to study ultrastructural plasticity of 7 distinct taxa and describe how subcellular organisation is linked to energy metabolism. %B Nature Communications %V 12 %P 1–12 %8 feb %G eng %U http://www.nature.com/articles/s41467-021-21314-0 %R 10.1038/s41467-021-21314-0 %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 The ISME Journal %D 2021 %T Viruses infecting a warm water picoeukaryote shed light on spatial co-occurrence dynamics of marine viruses and their hosts %A Bachy, Charles %A Yung, Charmaine C. M. %A Needham, David M. %A Gazitúa, Maria Consuelo %A Roux, Simon %A Limardo, Alexander J. %A Choi, Chang Jae %A Jorgens, Danielle M. %A Sullivan, Matthew B. %A Worden, Alexandra Z. %K RCC715 %K RCC716 %X The marine picoeukaryote Bathycoccus prasinos has been considered a cosmopolitan alga, although recent studies indicate two ecotypes exist, Clade BI (B. prasinos) and Clade BII. Viruses that infect Bathycoccus Clade BI are known (BpVs), but not that infect BII. We isolated three dsDNA prasinoviruses from the Sargasso Sea against Clade BII isolate RCC716. The BII-Vs do not infect BI, and two (BII-V2 and BII-V3) have larger genomes (\textasciitilde210 kb) than BI-Viruses and BII-V1. BII-Vs share \textasciitilde90% of their proteins, and between 65% to 83% of their proteins with sequenced BpVs. Phylogenomic reconstructions and PolB analyses establish close-relatedness of BII-V2 and BII-V3, yet BII-V2 has 10-fold higher infectivity and induces greater mortality on host isolate RCC716. BII-V1 is more distant, has a shorter latent period, and infects both available BII isolates, RCC716 and RCC715, while BII-V2 and BII-V3 do not exhibit productive infection of the latter in our experiments. Global metagenome analyses show Clade BI and BII algal relative abundances correlate positively with their respective viruses. The distributions delineate BI/BpVs as occupying lower temperature mesotrophic and coastal systems, whereas BII/BII-Vs occupy warmer temperature, higher salinity ecosystems. Accordingly, with molecular diagnostic support, we name Clade BII Bathycoccus calidus sp. nov. and propose that molecular diversity within this new species likely connects to the differentiated host-virus dynamics observed in our time course experiments. Overall, the tightly linked biogeography of Bathycoccus host and virus clades observed herein supports species-level host specificity, with strain-level variations in infection parameters. %B The ISME Journal %P 1–19 %8 may %G eng %U https://www.nature.com/articles/s41396-021-00989-9 %R 10.1038/s41396-021-00989-9 %0 Journal Article %J Scientific Reports %D 2020 %T Cryptic species in the parasitic Amoebophrya species complex revealed by a polyphasic approach %A Cai, Ruibo %A Kayal, Ehsan %A Alves-de-Souza, Catharina %A Bigeard, Estelle %A Corre, Erwan %A Jeanthon, Christian %A Marie, Dominique %A Porcel, Betina M %A Siano, Raffaele %A Szymczak, Jeremy %A Wolf, Matthias %A Guillou, Laure %K RCC1627 %K RCC1720 %K RCC3018 %K RCC3043 %K RCC3044 %K RCC3047 %K RCC3048 %K RCC3049 %K RCC3145 %K RCC3278 %K RCC3596 %K RCC4381 %K RCC4382 %K RCC4383 %K RCC4384 %K RCC4385 %K RCC4386 %K RCC4387 %K RCC4388 %K RCC4389 %K RCC4390 %K RCC4391 %K RCC4392 %K RCC4393 %K RCC4394 %K RCC4395 %K RCC4396 %K RCC4397 %K RCC4398 %K RCC4399 %K RCC4400 %K RCC4401 %K RCC4402 %K RCC4403 %K RCC4404 %K RCC4405 %K RCC4406 %K RCC4407 %K RCC4408 %K RCC4409 %K RCC4410 %K RCC4411 %K RCC4412 %K RCC4413 %K RCC4414 %K RCC4415 %K RCC4416 %K RCC4711 %K RCC4712 %K RCC4713 %K RCC4715 %K RCC4716 %K RCC4722 %K RCC4723 %K RCC4726 %K RCC4728 %K RCC4729 %K RCC4732 %K RCC4733 %K RCC4734 %K RCC5984 %K RCC5985 %K RCC5986 %K RCC5987 %K RCC5988 %K RCC5989 %K RCC5990 %K RCC5991 %K RCC5992 %K RCC5993 %K RCC5994 %K RCC5995 %K RCC5997 %K RCC5998 %K RCC5999 %K RCC6000 %K RCC6001 %K RCC6002 %K RCC6003 %K RCC6004 %K RCC6005 %K RCC6006 %K RCC6007 %K RCC6008 %K RCC6009 %K RCC6010 %K RCC6079 %K RCC6080 %K RCC6081 %K RCC6082 %K RCC6083 %K RCC6084 %K RCC6085 %K RCC6087 %K RCC6088 %K RCC6094 %K RCC6096 %K RCC6100 %K RCC6101 %K RCC6102 %K RCC6103 %K RCC6104 %K RCC6105 %K RCC6106 %K RCC6107 %K RCC6108 %K RCC6109 %K RCC6110 %K RCC6111 %K RCC6112 %K RCC6113 %K RCC6115 %K RCC6116 %K RCC6117 %K RCC6118 %K RCC6119 %K RCC6120 %K RCC6121 %B Scientific Reports %V 10 %P 2531 %8 dec %G eng %U http://dx.doi.org/10.1038/s41598-020-59524-z http://www.nature.com/articles/s41598-020-59524-z %R 10.1038/s41598-020-59524-z %0 Journal Article %J Science Advances %D 2020 %T Dimorphism in cryptophytes—The case of Teleaulax amphioxeia / Plagioselmis prolonga and its ecological implications %A Altenburger, A %A Blossom, H E %A Garcia-Cuetos, L. %A Jakobsen, H H %A Carstensen, J %A Lundholm, N. %A Hansen, P. J. %A Moestrup, Ø. %A Haraguchi, L. %K RCC5152 %X Growing evidence suggests that sexual reproduction might be common in unicellular organisms, but observations are sparse. Limited knowledge of sexual reproduction constrains understanding of protist ecology. Although Teleaulax amphioxeia and Plagioselmis prolonga are common marine cryptophytes worldwide, and are also important plastid donors for some kleptoplastic ciliates and dinoflagellates, the ecology and development of these protists are poorly known. We demonstrate that P. prolonga is the haploid form of the diploid T. amphioxeia and describe the seasonal dynamics of these two life stages. The diploid T. amphioxeia dominates during periods of high dissolved inorganic nitrogen (DIN) and low irradiance, temperature, and grazing (winter and early spring), whereas the haploid P. prolonga becomes more abundant during the summer, when DIN is low and irradiance, temperature, and grazing are high. Dimorphic sexual life cycles might explain the success of this species by fostering high genetic diversity and enabling endurance in adverse conditions. %B Science Advances %V 6 %P eabb1611 %8 sep %G eng %U https://advances.sciencemag.org/lookup/doi/10.1126/sciadv.abb1611 %R 10.1126/sciadv.abb1611 %0 Journal Article %J Toxics %D 2020 %T Effect of 10 UV filters on the brine shrimp Artemia salina and themarinemicroalga Tetraselmis sp. %A Thorel, Evane %A Clergeaud, Fanny %A Jaugeon, Lucie %A Rodrigues, Alice M.S. %A Lucas, Julie %A Stien, Didier %A Lebaron, Philippe %K Artemia salina %K marine environment %K Marine microalgae %K RCC500 %K Toxicity tests %K UV-filters %X The presence of pharmaceutical and personal care product (PPCP) residues in the aquatic environment is an emerging issue due to their uncontrolled release through gray water, and accumulation in the environment that may affect living organisms, ecosystems and public health. The aim of this study is to assess the toxicity of benzophenone-3 (BP-3), bis-ethylhexyloxyphenol methoxyphenyl triazine (BEMT), butyl methoxydibenzoylmethane (BM), methylene bis-benzotriazolyl tetramethylbutylphenol (MBBT), 2-ethylhexyl salicylate (ES), diethylaminohydroxybenzoyl hexyl benzoate (DHHB), diethylhexyl butamido triazone (DBT), ethylhexyl triazone (ET), homosalate (HS) and octocrylene (OC) on marine organisms from two major trophic levels, including autotrophs (Tetraselmis sp.) and heterotrophs (Artemia salina). In general, results showed that both HS and OC were the most toxic UV filters for our tested species, followed by a significant effect of BM on Artemia salina due to BM-but only at high concentrations (1 mg/L). ES, BP3 and DHHB affected the metabolic activity of the microalgae at 100 ??g/L. BEMT, DBT, ET, MBBT had no effect on the tested organisms, even at high concentrations (2 mg/L). OC toxicity represents a risk for those species, since concentrations used in this study are 15-90 times greater than those reported in occurrence studies for aquatic environments. For the first time in the literature, we report HS toxicity on a microalgae species at concentrations complementing those found in aquatic environments. These preliminary results could represent a risk in the future if concentrations of OC and HS continue to increase. %B Toxics %V 8 %P 29 %8 jun %G eng %U www.mdpi.com/journal/toxics %R 10.3390/TOXICS8020029 %0 Journal Article %J Ecology Letters %D 2020 %T Evolutionary temperature compensation of carbon fixation in marine phytoplankton %A Barton, Samuel %A Jenkins, James %A Buckling, Angus %A Schaum, C.-Elisa %A Smirnoff, Nicholas %A Raven, John A. %A Yvon-Durocher, Gabriel %E Ezenwa, Vanessa %K climate change %K evolutionary ecology %K metabolism %K phytoplankton physiology %K RCC1303 %K rcc1512 %K RCC1773 %K RCC4221 %K RCC623 %K RCC626 %K RCC652 %K RCC80 %K RCC834 %K thermal performance curves %X The efficiency of carbon sequestration by the biological pump could decline in the coming decades because respiration tends to increase more with temperature than photosynthesis. Despite these differences in the short-term temperature sensitivities of photosynthesis and respiration, it remains unknown whether the long-term impacts of global warming on metabolic rates of phytoplankton can be modulated by evolutionary adaptation. We found that respiration was consistently more temperature dependent than photosynthesis across 18 diverse marine phytoplankton, resulting in universal declines in the rate of carbon fixation with short-term increases in temperature. Long-term experimental evolution under high temperature reversed the short-term stimulation of metabolic rates, resulting in increased rates of carbon fixation. Our findings suggest that thermal adaptation may therefore have an ameliorating impact on the efficiency of phytoplankton as primary mediators of the biological carbon pump. %B Ecology Letters %P ele.13469 %8 feb %G eng %U https://onlinelibrary.wiley.com/doi/abs/10.1111/ele.13469 %R 10.1111/ele.13469 %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 bioRxiv %D 2020 %T In-cell quantitative structural imaging of phytoplankton using 3D electron microscopy %A Uwizeye, Clarisse %A Decelle, Johan %A Jouneau, Pierre-Henri %A Gallet, Benoit %A Keck, Jean-baptiste %A Schwab, Yannick %A Schoehn, Guy %A Zeeman, Samuel C %A Falconet, Denis %A Finazzi, Giovanni %A Moriscot, Christine %A Chevalier, Fabien %A Schieber, Nicole L %A Templin, Rachel %A Curien, Gilles %A Schwab, Yannick %A Schoehn, Guy %A Zeeman, Samuel C %A Falconet, Denis %A Finazzi, Giovanni %K RCC100 %K RCC4014 %K RCC827 %K RCC909 %X Phytoplankton is a minor fraction of the global biomass playing a major role in primary production and climate. Despite improved understanding of phytoplankton diversity and genomics, we lack nanoscale subcellular imaging approaches to understand their physiology and cell biology. Here, we present a complete Focused Ion Beam - Scanning Electron Microscopy (FIB-SEM) workflow (from sample preparation to image processing) to generate nanometric 3D phytoplankton models. Tomograms of entire cells, representatives of six ecologically-successful phytoplankton unicellular eukaryotes, were used for quantitative morphometric analysis. Besides lineage-specific cellular architectures, we observed common features related to cellular energy management: i) conserved cell-volume fractions occupied by the different organelles; ii) consistent plastid-mitochondria interactions, iii) constant volumetric ratios in these energy-producing organelles. We revealed detailed subcellular features related to chromatin organization and to biomineralization. Overall, this approach opens new perspectives to study phytoplankton acclimation responses to abiotic and biotic factors at a relevant biological scale.Competing Interest StatementThe authors have declared no competing interest. %B bioRxiv %P 2020.05.19.104166 %8 jan %G eng %U http://biorxiv.org/content/early/2020/05/20/2020.05.19.104166.abstract %R 10.1101/2020.05.19.104166 %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 Philosophical transactions. Series A, Mathematical, physical, and engineering sciences %D 2020 %T Use of organic exudates from two polar diatoms by bacterial isolates from the Arctic Ocean %A Tisserand, Lucas %A Dadaglio, Laëtitia %A Intertaglia, Laurent %A Catala, Philippe %A Panagiotopoulos, Christos %A Obernosterer, Ingrid %A Joux, Fabien %K Arctic Ocean %K bacterial diversity %K bacterial isolation %K biodegradation %K diatoms %K dissolved organic exudates %K RCC2278 %K RCC4289 %X Global warming affects primary producers in the Arctic, with potential consequences for the bacterial community composition through the consumption of microalgae-derived dissolved organic matter (DOM). To determine the degree of specificity in the use of an exudate by bacterial taxa, we used simple microalgae-bacteria model systems. We isolated 92 bacterial strains from the sea ice bottom and the water column in spring-summer in the Baffin Bay (Arctic Ocean). The isolates were grouped into 42 species belonging to Proteobacteria, Bacteroidetes, Actinobacteria and Firmicutes. Forty strains were tested for their capacity to grow on the exudate from two Arctic diatoms. Most of the strains tested (78%) were able to grow on the exudate from the pelagic diatom Chaetoceros neogracilis, and 33% were able to use the exudate from the sea ice diatom Fragilariopsis cylindrus. 17.5% of the strains were not able to grow with any exudate, while 27.5% of the strains were able to use both types of exudates. All strains belonging to Flavobacteriia (n = 10) were able to use the DOM provided by C. neogracilis, and this exudate sustained a growth capacity of up to 100 times higher than diluted Marine Broth medium, of two Pseudomonas sp. strains and one Sulfitobacter strain. The variable bioavailability of exudates to bacterial strains highlights the potential role of microalgae in shaping the bacterial community composition. This article is part of the theme issue 'The changing Arctic Ocean: consequences for biological communities, biogeochemical processes and ecosystem functioning'. %B Philosophical transactions. Series A, Mathematical, physical, and engineering sciences %V 378 %P 20190356 %8 oct %G eng %U https://royalsocietypublishing.org/doi/10.1098/rsta.2019.0356 %R 10.1098/rsta.2019.0356 %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 PLOS ONE %D 2019 %T Relationship between coccolith length and thickness in the coccolithophore species Emiliania huxleyi and Gephyrocapsa oceanica %A Linge Johnsen, Simen Alexander %A Bollmann, Jörg %A Gebuehr, Christina %A Herrle, Jens O. %E Keller, David Peter %K rcc1210 %K RCC1223 %K RCC1232 %K rcc1824 %K rcc1843 %K rcc868 %B PLOS ONE %V 14 %P e0220725 %8 aug %G eng %U http://dx.plos.org/10.1371/journal.pone.0220725 %R 10.1371/journal.pone.0220725 %0 Journal Article %J New Phytologist %D 2019 %T Unveiling membrane thermoregulation strategies in marine picocyanobacteria %A Breton, Solène %A Jouhet, Juliette %A Guyet, Ulysse %A Gros, Valérie %A Pittera, Justine %A Demory, David %A Partensky, Frédéric %A Doré, Hugo %A Ratin, Morgane %A Maréchal, Éric %A Nguyen, Ngoc An %A Garczarek, Laurence %A Six, Christophe %K RCC2374 %K RCC2385 %K RCC515 %K rcc539 %B New Phytologist %P nph.16239 %8 oct %G eng %U https://onlinelibrary.wiley.com/doi/abs/10.1111/nph.16239 %R 10.1111/nph.16239 %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 Microbiology %D 2018 %T Bacterial epibiotic communities of ubiquitous and abundant marine diatoms are distinct in short- and long-term associations %A Crenn, Klervi %A Duffieux, Delphine %A Jeanthon, Christian %K 2018 %K Chaetoceros %K diatoms %K diversity %K heterotrophic bacteria %K interactions %K microbiome %K rcc %K RCC2560 %K RCC2565 %K Thalassiosira %K Western English Channel %X Interactions between phytoplankton and bacteria play a central role in mediatingbiogeochemical cycling and food web structure in the ocean. The cosmopolitan diatomsThalassiosiraandChaetocerosoften dominate phytoplankton communities in marinesystems. Past studies of diatom-bacterial associations have employed community-level methods and culture-based or natural diatom populations. Although bacterialassemblages attached to individual diatoms represents tight associations little is knownon their makeup or interactions. Here, we examined the epibiotic bacteria of 436Thalassiosiraand 329Chaetocerossingle cells isolated from natural samples andcollection cultures, regarded here as short- and long-term associations, respectively.Epibiotic microbiota of single diatom hosts was analyzed by cultivation and by cloning-sequencing of 16S rRNA genes obtained from whole-genome amplification products.The prevalence of epibiotic bacteria was higher in cultures and dependent of the hostspecies. Culture approaches demonstrated that both diatoms carry distinct bacterialcommunities in short- and long-term associations. Bacterial epibonts, commonlyassociated with phytoplankton, were repeatedly isolated from cells of diatom collectioncultures but were not recovered from environmental cells. Our results suggest thatin controlled laboratory culture conditions bacterial–diatom and bacterial–bacterialinteractions select for a simplified, but specific, epibiotic microbiota shaped and adaptedfor long-term associations. %B Frontiers in Microbiology %V 9 %P 1–12 %G eng %U https://www.frontiersin.org/article/10.3389/fmicb.2018.02879/full %R 10.3389/fmicb.2018.02879 %0 Journal Article %J Aquatic Microbial Ecology %D 2018 %T Differential responses of bacteria to diatom-derived dissolved organic matter in the Arctic Ocean %A Dadaglio, L %A Dinasquet, J %A Obernosterer, I %A Joux, F %K 2018 %K rcc %X ABSTRACT: The Arctic sea ice cover is undergoing an unprecedented decline due to climate change. This loss may result in the earlier start of ice algae blooms and more intense phytoplankton blooms, leading to higher concentrations of dissolved organic matter (DOM) derived from primary production. We investigated the response of early summer Arctic bacterial communities to the addition of Arctic diatom-derived DOM through biodegradation experiments in Baffin Bay. DOM produced by the planktonic diatom Chaetoceros neogracilis and the sea ice diatom Fragilariopsis cylindrus was added to seawater from 3 stations with different ice cover (2 ice zones and 1 open water zone) for 12 d. At the 3 stations, the addition of inorganic nutrients (PO4 and NO3) was not sufficient to stimulate bacterial growth compared to the controls, suggesting that bacteria were mainly limited by organic carbon. The addition of DOM from C. neogracilis stimulated bacterial abundance and production, with a more pronounced response in the ice zone compared to the open water zone. The enhanced bacterial metabolism was accompanied by changes in the bacterial community composition determined by 16S rRNA sequencing, driven by operational taxonomic units (OTUs) related to Pseudoalteromonas and Polaribacter that increased in relative abundance with DOM addition. Moreover, in the ice zone, DOM from C. neogracilis induced a priming effect on the bacterial utilization of ambient DOM. Our findings suggest that phytoplankton blooms, through the production of labile organic matter, will strongly affect bacterial heterotrophic activity, composition and dissolved organic carbon cycling in the Arctic Ocean. %B Aquatic Microbial Ecology %V 82 %P 59–72 %G eng %U https://www.int-res.com/abstracts/ame/v82/n1/p59-72 %R 10.3354/ame01883 %0 Journal Article %J PLOS ONE %D 2018 %T Temperature effects on sinking velocity of different Emiliania huxleyi strains %A Rosas-Navarro, Anaid %A Langer, Gerald %A Ziveri, Patrizia %E Johnson, Colin %K IAN01 %K rcc1252 %K rcc1710 %X The sinking properties of three strains of Emiliania huxleyi in response to temperature changes were examined. We used a recently proposed approach to calculate sinking velocities from coccosphere architecture, which has the advantage to be applicable not only to culture samples, but also to field samples including fossil material. Our data show that temperature in the sub-optimal range impacts sinking velocity of E. huxleyi. This response is widespread among strains isolated in different locations and moreover comparatively predictable, as indicated by the similar slopes of the linear regressions. Sinking velocity was positively correlated to temperature as well as individual cell PIC/POC over the sub-optimum to optimum temperature range in all strains. In the context of climate change our data point to an important influence of global warming on sinking velocities. It has recently been shown that seawater acidification has no effect on sinking velocity of a Mediterranean E. huxleyi strain, while nutrient limitation seems to have a small negative effect on sinking velocity. Given that warming, acidification, and lowered nutrient availability will occur simultaneously under climate change scenarios, the question is what the net effect of different influential factors will be. For example, will the effects of warming and nutrient limitation cancel? This question cannot be answered conclusively but analyses of field samples in addition to laboratory culture studies will improve predictions because in field samples multi-factor influences and even evolutionary changes are not excluded. As mentioned above, the approach of determining sinking rate followed here is applicable to field samples. Future studies could use it to analyse not only seasonal and geographic patterns but also changes in sinking velocity over geological time scales. %B PLOS ONE %V 13 %P e0194386 %G eng %U http://dx.plos.org/10.1371/journal.pone.0194386 %R 10.1371/journal.pone.0194386 %0 Journal Article %J Frontiers in Microbiology %D 2017 %T Diverse CO2-Induced responses in physiology and gene expression among eukaryotic phytoplankton %A Hennon, Gwenn M. M. %A Hernández Limón, María D. %A Haley, Sheean T. %A Juhl, Andrew R. %A Dyhrman, Sonya T. %K algae %K biophysical CCM %K C4 CCM %K carbon concentrating mechanism %K carbon concentrating mechanism (CCM) %K ccm %K photorespiration %K RCC1303 %K transcriptomics %X With rising atmospheric CO2, phytoplankton face shifts in ocean chemistry including increased dissolved CO2 and acidification that will likely influence the relative competitive fitness of different phytoplankton taxa. Here we compared the physiological and gene expression responses of six species of phytoplankton including a diatom, a raphidophyte, two haptophytes, and two dinoflagellates to ambient (\~400 ppm) and elevated (\~800 ppm) CO2. Dinoflagellates had significantly slower growth rates and higher, yet variable, chlorophyll a per cell under elevated CO2. The other phytoplankton tended to have increased growth rates and/or decreased chlorophyll a per cell. Carbon and nitrogen partitioning of cells shifted under elevated CO2 in some species, indicating potential changes in energy fluxes due to changes in carbon concentrating mechanisms (CCM) or photorespiration. Consistent with these phenotypic changes, gene set enrichment analyses revealed shifts in energy, carbon and nitrogen metabolic pathways, though with limited overlap between species in the genes and pathways involved. Similarly, gene expression responses across species revealed few conserved CO2-responsive genes within CCM and photorespiration categories, and a survey of available transcriptomes found high diversity in biophysical CCM and photorespiration expressed gene complements between and within the four phyla represented by these species. The few genes that displayed similar responses to CO2 across phyla were from understudied gene families, making them targets for further research to uncover the mechanisms of phytoplankton acclimation to elevated CO2. These results underscore that eukaryotic phytoplankton have diverse gene complements and gene expression responses to CO2 perturbations and highlight the value of cross-phyla comparisons for identifying gene families that respond to environmental change. %B Frontiers in Microbiology %V 8 %P 1–14 %8 dec %G eng %U http://journal.frontiersin.org/article/10.3389/fmicb.2017.02547/full %R 10.3389/fmicb.2017.02547 %0 Journal Article %J Plant Physiology %D 2017 %T Glycerolipid characterization and nutrient deprivation-associated changes in the green picoalga ostreococcus tauri %A Degraeve-Guilbault, Charlotte %A Bréhélin, Claire %A Haslam, Richard %A Sayanova, Olga %A Marie-Luce, Glawdys %A Jouhet, Juliette %A Corellou, Florence %K rcc3401 %K RCC4222 %K RCC745 %K RCC788 %K RCC789 %K RCC802 %K RCC809 %K RCC834 %X The picoalga Ostreococcus tauri is a minimal photosynthetic eukaryote that has been used as a model system. O. tauri is known to efficiently produce docosahexaenoic acid (DHA). We provide a comprehensive study of the glycerolipidome of O. tauri and validate this species as model for related picoeukaryotes. O. tauri lipids displayed unique features that combined traits from the green and the chromalveolate lineages. The betaine lipid diacylglyceryl-hydroxymethyl-trimethyl-β-alanine and phosphatidyldimethylpropanethiol, both hallmarks of chromalveolates, were identified as presumed extraplastidial lipids. DHA was confined to these lipids, while plastidial lipids of prokaryotic type were characterized by the overwhelming presence of ω-3 C18 polyunsaturated fatty acids (FAs), 18:5 being restricted to galactolipids. C16:4, an FA typical of green microalgae galactolipids, also was a major component of O. tauri extraplastidial lipids, while the 16:4-coenzyme A (CoA) species was not detected. Triacylglycerols (TAGs) displayed the complete panel of FAs, and many species exhibited combinations of FAs diagnostic for plastidial and extraplastidial lipids. Importantly, under nutrient deprivation, 16:4 and ω-3 C18 polyunsaturated FAs accumulated into de novo synthesized TAGs while DHA-TAG species remained rather stable, indicating an increased contribution of FAs of plastidial origin to TAG synthesis. Nutrient deprivation further severely down-regulated the conversion of 18:3 to 18:4, resulting in obvious inversion of the 18:3/18:4 ratio in plastidial lipids, TAGs, as well as acyl-CoAs. The fine-tuned and dynamic regulation of the 18:3/18:4 ratio suggested an important physiological role of these FAs in photosynthetic membranes. Acyl position in structural and storage lipids together with acyl-CoA analysis further help to determine mechanisms possibly involved in glycerolipid synthesis. %B Plant Physiology %V 173 %P 2060–2080 %G eng %U http://www.plantphysiol.org/lookup/doi/10.1104/pp.16.01467 %R 10.1104/pp.16.01467 %0 Journal Article %J Harmful Algae %D 2017 %T Mixotrophy in the marine red-tide cryptophyte Teleaulax amphioxeia and ingestion and grazing impact of cryptophytes on natural populations of bacteria in Korean coastal waters %A Yoo, Yeong Du %A Seong, Kyeong Ah %A Jeong, Hae Jin %A Yih, Wonho %A Rho, Jung Rae %A Nam, Seung Won %A Kim, Hyung Seop %K Bloom %K Flagellate %K Grazing impact %K Predator-prey relationship %K RCC1086 %K Red tide %X Cryptophytes are ubiquitous and one of the major phototrophic components in marine plankton communities. They often cause red tides in the waters of many countries. Understanding the bloom dynamics of cryptophytes is, therefore, of great importance. A critical step in this understanding is unveiling their trophic modes. Prior to this study, several freshwater cryptophyte species and marine Cryptomonas sp. and Geminifera cryophila were revealed to be mixotrophic. The trophic mode of the common marine cryptophyte species, Teleaulax amphioxeia has not been investigated yet. Thus, to explore the mixotrophic ability of T. amphioxeia by assessing the types of prey species that this species is able to feed on, the protoplasms of T. amphioxeia cells were carefully examined under an epifluorescence microscope and a transmission electron microscope after adding each of the diverse prey species. Furthermore, T. amphioxeia ingestion rates heterotrophic bacteria and the cyanobacterium Synechococcus sp. were measured as a function of prey concentration. Moreover, the feeding of natural populations of cryptophytes on natural populations of heterotrophic bacteria was assessed in Masan Bay in April 2006. This study reported for the first time, to our knowledge, that T. amphioxeia is a mixotrophic species. Among the prey organisms offered, T. amphioxeia fed only on heterotrophic bacteria and Synechococcus sp. The ingestion rates of T. amphioxeia on heterotrophic bacteria or Synechococcus sp. rapidly increased with increasing prey concentrations up to 8.6 × 106 cells ml-1, but slowly at higher prey concentrations. The maximum ingestion rates of T. amphioxeia on heterotrophic bacteria and Synechococcus sp. reached 0.7 and 0.3 cells predator-1 h-1, respectively. During the field experiments, the ingestion rates and grazing coefficients of cryptophytes on natural populations of heterotrophic bacteria were 0.3–8.3 cells predator-1 h-1 and 0.012–0.033 d-1, respectively. Marine cryptophytes, including T. amphioxeia, are known to be favorite prey species for many mixotrophic and heterotrophic dinoflagellates and ciliates. Cryptophytes, therefore, likely play important roles in marine food webs and may exert a considerable potential grazing impact on the populations of marine bacteria. %B Harmful Algae %V 68 %P 105–117 %G eng %U http://dx.doi.org/10.1016/j.hal.2017.07.012 %R 10.1016/j.hal.2017.07.012 %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 Temperature is a key factor in Micromonas–virus interactions %A Demory, David %A Arsenieff, Laure %A Simon, Nathalie %A Six, Christophe %A Rigaut-jalabert, Fabienne %A Marie, Dominique %A Ge, Pei %A Bigeard, Estelle %A Jacquet, Stéphan %A Sciandra, Antoine %A Bernard, Olivier %A Rabouille, Sophie %A Baudoux, Anne-claire %K 2017 %K RCC4229 %K RCC4253 %K RCC4265 %K RCC451 %K RCC829 %K RCC834 %K sbr?hyto$_\textrmd$ipo %K sbr?hyto?app %X The genus Micromonas comprises phytoplankton that show among the widest latitudinal distributions on Earth, and members of this genus are recurrently infected by prasinoviruses in contrasted thermal ecosystems. In this study, we assessed how temperature influences the interplay between the main genetic clades of this prominent microalga and their viruses. The growth of three Micromonas strains (Mic-A, Mic-B, Mic-C) and the stability of their respective lytic viruses (MicV-A, MicV-B, MicV-C) were measured over a thermal range of 4–32.5 °C. Similar growth temperature optima (Topt) were predicted for all three hosts but Mic-B exhibited a broader thermal tolerance than Mic-A and Mic-C, suggesting distinct thermoacclimation strategies. Similarly, the MicV-C virus displayed a remarkable thermal stability compared with MicV-A and MicV-B. Despite these divergences, infection dynamics showed that temperatures below Topt lengthened lytic cycle kinetics and reduced viral yield and, notably, that infection at temperatures above Topt did not usually result in cell lysis. Two mechanisms operated depending on the temperature and the biological system. Hosts either prevented the production of viral progeny or maintained their ability to produce virions with no apparent cell lysis, pointing to a possible switch in the viral life strategy. Hence, temperature changes critically affect the outcome of Micromonas infection and have implications for ocean biogeochemistry and evolution. %B The ISME Journal %V 11 %P 601–612 %8 mar %G eng %U http://dx.doi.org/10.1038/ismej.2016.160 http://www.nature.com/doifinder/10.1038/ismej.2016.160 %R 10.1038/ismej.2016.160 %0 Journal Article %J Applied and Environmental Microbiology %D 2016 %T Abundance and biogeography of picoprasinophyte ecotypes and other phytoplankton in the eastern north pacific ocean %A Simmons, Melinda P. %A Sudek, Sebastian %A Monier, Adam %A Limardo, Alexander J. %A Jimenez, Valeria %A Perle, Christopher R. %A Elrod, Virginia A. %A Pennington, J. Timothy %A Worden, Alexandra Z. %E Schloss, P. D. %K 2016 %K rcc %X Eukaryotic algae within the picoplankton size class (<=2 ??m in diameter) are important marine primary producers, but their spatial and ecological distributions are not well characterized. Here, we studied three picoeukaryotic prasinophyte genera and their cyanobacterial counterparts, Prochlorococcus and Synechococcus , during two cruises along a North Pacific transect characterized by different ecological regimes. Picoeukaryotes and Synechococcus reached maximum abundances of 1.44 × 10 5 and 3.37 × 10 5 cells ? ml -1 , respectively, in mesotrophic waters, while Prochlorococcus reached 1.95 × 10 5 cells ? ml -1 in the oligotrophic ocean. Of the picoeukaryotes, Bathycoccus was present at all stations in both cruises, reaching 21,368 ± 327 18S rRNA gene copies ? ml -1 . Micromonas and Ostreococcus clade OI were detected only in mesotrophic and coastal waters and Ostreococcus clade OII only in the oligotrophic ocean. To resolve proposed Bathycoccus ecotypes, we established genetic distances for 1,104 marker genes using targeted metagenomes and the Bathycoccus prasinos genome. The analysis was anchored in comparative genome analysis of three Ostreococcus species for which physiological and environmental data are available to facilitate data interpretation. We established that two Bathycoccus ecotypes exist, named here BI (represented by coastal isolate Bathycoccus prasinos ) and BII. These share 82% ± 6% nucleotide identity across homologs, while the Ostreococcus spp. share 75% ± 8%. We developed and applied an analysis of ecomarkers to metatranscriptomes sequenced here and published -omics data from the same region. The results indicated that the Bathycoccus ecotypes cooccur more often than Ostreococcus clades OI and OII do. Exploratory analyses of relative transcript abundances suggest that Bathycoccus NRT2.1 and AMT2.2 are high-affinity NO 3 - and low-affinity NH 4 + transporters, respectively, with close homologs in multiple picoprasinophytes. Additionally, in the open ocean, where dissolved iron concentrations were low (0.08 nM), there appeared to be a shift to the use of nickel superoxide dismutases (SODs) from Mn/Fe/Cu SODs closer inshore. Our study documents the distribution of picophytoplankton along a North Pacific ecological gradient and offers new concepts and techniques for investigating their biogeography. %B Applied and Environmental Microbiology %V 82 %P 1693–1705 %8 mar %G eng %U http://aem.asm.org/lookup/doi/10.1128/AEM.02730-15 %R 10.1128/AEM.02730-15 %0 Journal Article %J Nature Communications %D 2016 %T Decrease in coccolithophore calcification and CO2 since the middle Miocene %A Bolton, Clara T. %A Hernández-Sánchez, María T. %A Fuertes, Miguel-Ángel %A González-Lemos, Saúl %A Abrevaya, Lorena %A Méndez-Vicente, Ana %A Flores, José-Abel %A Probert, Ian %A Giosan, Liviu %A Johnson, Joel %A Stoll, Heather M. %K 2016 %K rcc %X Marine algae are instrumental in carbon cycling and atmospheric carbon dioxide (CO2) regulation. One group, coccolithophores, uses carbon to photosynthesize and to calcify, covering their cells with chalk platelets (coccoliths). How ocean acidification influences coccolithophore calcification is strongly debated, and the effects of carbonate chemistry changes in the geological past are poorly understood. This paper relates degree of coccolith calcification to cellular calcification, and presents the first records of size-normalized coccolith thickness spanning the last 14 Myr from tropical oceans. Degree of calcification was highest in the low-pH, high-CO2 Miocene ocean, but decreased significantly between 6 and 4 Myr ago. Based on this and concurrent trends in a new alkenone ep record, we propose that decreasing CO2 partly drove the observed trend via reduced cellular bicarbonate allocation to calcification. This trend reversed in the late Pleistocene despite low CO2, suggesting an additional regulator of calcification such as alkalinity. 1 %B Nature Communications %V 7 %P 10284 %G eng %U http://www.nature.com/doifinder/10.1038/ncomms10284 %R 10.1038/ncomms10284 %0 Journal Article %J Applied and Environmental Microbiology %D 2016 %T The geographic impact on genomic divergence as revealed by comparison of nine Citromicrobial genomes %A Zheng, Qiang %A Liu, Yanting %A Jeanthon, Christian %A Zhang, Rui %A Lin, Wenxin %A Yao, Jicheng %A Jiao, Nianzhi %K 2016 %K RCC1878 %K RCC1885 %K RCC1897 %K sbr?hyto?app %X Aerobic anoxygenic phototrophic bacteria (AAPB) are thought to be important players in oceanic carbon and energy cycling in the euphotic zone of the ocean. The genus Citromicrobium , widely found in oligotrophic oceans, is a member of marine alphaproteobacterial AAPB. Nine Citromicrobium strains isolated from the South China Sea, the Mediterranean Sea or the tropical South Atlantic were found to harbor identical 16S rRNA sequences. The sequencing of their genomes revealed high synteny in major regions. Nine genetic islands (GIs), involved mainly in type IV secretion systems, flagellar biosynthesis, prophage and integrative conjugative elements, were identified by a fine scale comparative genomics analysis. These GIs played significant roles in genomic evolution and divergence. Interestingly, the co-existence of two different photosynthetic gene clusters (PGCs) was not only found in the analyzed genomes but also confirmed, for the first time, in environmental samples. The prevalence of the coexistence of two different PGCs may suggest an adaptation mechanism for Citromicrobium members to survive in the oceans. Comparison of genomic characteristics (e.g., GIs, ANI, SNPs and phylogeny) revealed that strains within a marine region shared a similar evolutionary history that was distinct from that of strains isolated from other regions (South China Sea vs Mediterranean Sea). Geographic differences are partly responsible for driving the observed genomic divergences, and allow microbes to evolve through local adaptation. Three Citromicrobium strains isolated from the Mediterranean Sea diverged millions of years ago from other strains, and evolved into a novel group. %B Applied and Environmental Microbiology %V 82 %P AEM.02495–16 %G eng %U http://aem.asm.org/lookup/doi/10.1128/AEM.02495-16 %R 10.1128/AEM.02495-16 %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 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 Molecular ecology %D 2016 %T Transcriptomic profiling of Alexandrium fundyense during physical interaction with or exposure to chemical signals from the parasite Amoebophrya. %A Lu, Yameng %A Wohlrab, Sylke %A Groth, Marco %A Glöckner, Gernot %A Guillou, Laure %A John, Uwe %K 2016 %K Animals %K Dinoflagellida %K Dinoflagellida: genetics %K Dinoflagellida: parasitology %K Gene Expression Profiling %K Harmful Algal Bloom %K Host-Parasite Interactions %K Metabolic Networks and Pathways %K Microalgae %K Microalgae: genetics %K Microalgae: parasitology %K Parasites %K Parasites: chemistry %K RCC3037 %K RNA %K Sequence Analysis %K Signal Transduction %K Transcriptome %X Toxic microalgae have their own pathogens, and understanding the way in which these microalgae respond to antagonistic attacks may provide information about their capacity to persist during harmful algal bloom events. Here, we compared the effects of the physical presence of the parasite Amoebophrya sp. and exposure to waterborne cues from cultures infected with this parasite, on gene expression by the toxic dinoflagellates, Alexandrium fundyense. Compared with control samples, a total of 14,882 Alexandrium genes were differentially expressed over the whole-parasite infection cycle at three different time points (0, 6 and 96 h). RNA sequencing analyses indicated that exposure to the parasite and parasitic waterborne cues produced significant changes in the expression levels of Alexandrium genes associated with specific metabolic pathways. The observed upregulation of genes associated with glycolysis, the tricarboxylic acid cycle, fatty acid β-oxidation, oxidative phosphorylation and photosynthesis suggests that parasite infection increases the energy demand of the host. The observed upregulation of genes correlated with signal transduction indicates that Alexandrium could be sensitized by parasite attacks. This response might prime the defence of the host, as indicated by the increased expression of several genes associated with defence and stress. Our findings provide a molecular overview of the response of a dinoflagellate to parasite infection. %B Molecular ecology %V 25 %P 1294–307 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/26841307 %R 10.1111/mec.13566 %0 Journal Article %J Algae %D 2015 %T Morphology , molecular phylogeny , and pigment characterization of a novel phenotype of the dinoflagellate genus Pelagodinium from Korean waters %A Potvin, Éric %A Jeong, Hae Jin %A Kang, Nam Seon %A Noh, Jae Hoon %A Yang, Eun Jin %K foraminifera %K gymnodinium bei %K pelagic symbiont %K rcc %K suessiaceae %K suessiales %X The dinoflagellate genus Pelagodinium is genetically classified in distinct sub-clades and subgroups. However, it is dif- ficult to determine whether this genetic diversity represents intra- or interspecific divergence within the genus since only the morphology of the type strain of the genus Pelagodinium, Pelagodinium bei, is available. An isolate associated with the genus Pelagodinium from Shiwha Bay, Korea, was recently cultured. This isolate formed a subgroup with 3 to 4 strains from the Atlantic Ocean, Mediterranean Sea, and Indian Ocean. This subgroup was distinct from the subgroup contain- ing P. bei. The morphology of the isolate was analyzed using optical and scanning electron microscopy and was almost identical to that of P. bei except that this isolate had two series of amphiesmal vesicles (AVs) in the cingulum, unlike P. bei that has one series. When the pigment compositions of the isolate and P. bei were analyzed using high-performance liquid chromatography, these two strains had peridinin as a major accessory pigment and their pigment compositions were almost identical. In addition, the swimming behaviors of these two strains were very similar. The re-examination of the type culture of P. bei revealed two series in the cingulum as for the isolate. The new findings on the number of series of AVs in the cingulum, the pigment composition, and the swimming behaviors suggest that P. bei and the isolate may be conspecific despite their association to genetically different subgroups. This study provides a basis to further understand the molecular classification within Pelagodinium combining genetic, morphological, pigment, and behavioral data. %B Algae %V 30 %P 183–195 %G eng %R 10.4490/algae.2015.30.3.183 %0 Journal Article %J Frontiers in Microbiology %D 2015 %T Paralytic shellfish toxin content is related to genomic sxtA4 copy number in Alexandrium minutum strains %A Stüken, Anke %A Riobó, Pilar %A Franco, José %A Jakobsen, Kjetill S. %A Guillou, Laure %A Figueroa, Rosa I. %K 2015 %K Alexandrium %K copy %K copy number variation %K Dinoflagellate %K gene dosage %K genome size %K number variation %K paralytic shellfish toxin %K paralytic shellfish toxin (PST) %K pst %K rcc %K RCC?o?dd %K saxitoxin %K saxitoxin (STX) %K sbr?hyto$_\textrmd$ipo %K stx %K sxtA %X Dinoflagellates are microscopic aquatic eukaryotes with huge genomes and an unusual cell regulation. For example, most genes are present in numerous copies and all copies seem to be obligatorily transcribed. The consequence of the gene copy number (CPN) for final protein synthesis is, however, not clear. One such gene is sxtA, the starting gene of paralytic shellfish toxin (PST) synthesis. PSTs are small neurotoxic compounds that can accumulate in the food chain and cause serious poisoning incidences when ingested. They are produced by dinoflagellates of the genera Alexandrium, Gymnodium, and Pyrodinium. Here we investigated if the genomic CPN of sxtA4 is related to PST content in Alexandrium minutum cells. SxtA4 is the 4th domain of the sxtA gene and its presence is essential for PST synthesis in dinoflagellates. We used PST and genome size measurements as well as quantitative PCR to analyze sxtA4 CPN and toxin content in 15 A. minutum strains. Our results show a strong positive correlation between the sxtA4 CPN and the total amount of PST produced in actively growing A. minutum cells. This correlation was independent of the toxin profile produced, as long as the strain contained the genomic domains sxtA1 and sxtA4. %B Frontiers in Microbiology %V 6 %P 1–10 %G eng %U http://journal.frontiersin.org/article/10.3389/fmicb.2015.00404 %R 10.3389/fmicb.2015.00404 %0 Journal Article %J Protist %D 2014 %T Dinomyces arenysensis gen. et sp. nov. (rhizophydiales, dinomycetaceae fam. nov.), a chytrid infecting marine dinoflagellates %A Lepelletier, Frédéric %A Karpov, Sergey A %A Alacid, Elisabet %A Le Panse, Sophie %A Bigeard, Estelle %A Garcés, Esther %A Jeanthon, Christian %A Guillou, Laure %K 2014 %K chytrid %K Dinoflagellates %K Dinomyces arenysensis %K Fungi %K MACUMBA %K microbial parasitoids %K rcc %K RCC?o?dd %K Rhizophydiales. %K SBR$_\textrmP$hyto$_\textrmD$PO %K sbr?hyto$_\textrmd$ipo %K sbr?hyto?app %X Environmental 18S rRNA gene surveys of microbial eukaryotes have recently revealed the diversity of major parasitic agents in pelagic freshwater systems, consisting primarily of chytrid fungi. To date, only a few studies have reported the presence of chydrids in the marine environment and a limited number of marine chytrids have been properly identified and characterized. Here, we report the isolation and cultivation of a marine chytrid from samples taken during a bloom of the toxic dinoflagellate Alexandrium minutum in the Arenys de Mar harbour (Mediterranean Sea, Spain). Cross-infections using cultures and natural phytoplankton communities revealed that this chytrid is only able to infect certain species of dinoflagellates, with a rather wide host range but with a relative preference for Alexandrium species. Phylogenetic analyses showed that it belongs to the order Rhizophydiales, but cannot be included in any of the existing families within this order. Several ultrastructural characters confirmed the placement of this taxon within the Rhizophydiales as well its novelty notably in terms of zoospore structure. This marine chytridial parasitoid is described as a new genus and species, Dinomyces arenysensis, within the Dinomycetaceae fam. nov. %B Protist %V 165 %P 230–244 %G eng %U http://www.sciencedirect.com/science/article/pii/S1434461014000170 %R 10.1016/j.protis.2014.02.004 %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 Protist %D 2014 %T Parvilucifera rostrata sp. nov., a novel parasite in the phylum Perkinsozoa that infects the toxic dinoflagellate Alexandrium minutum (Dinophyceae) %A Lepelletier, F %A Karpov, S A %A Le Panse, S %A Bigeard, E %A Skovgaard, A %A Jeanthon, C %A Guillou, L %K 2014 %K MACUMBA %K rcc %K SBR$_\textrmP$hyto$_\textrmD$PO %K SBR$_\textrmP$hyto$_\textrmP$PM %K sbr?hyto$_\textrmd$ipo %K sbr?hyto?app %B Protist %V 165 %P 31–49 %G eng %R 10.1016/j.protis.2013.09.005 %0 Journal Article %J Chinese Journal of Oceanology and Limnology %D 2013 %T Genetic transformation of marine cyanobacterium Synechococcus sp. CC9311 (Cyanophyceae) by electroporation %A Chen, Huaxin %A Lin, Hanzhi %A Jiang, Peng %A Li, Fuchao %A Qin, Song %K RCC1086 %X Synechococcus sp. CC9311 is a marine cyanobacterium characterized by type IV chromatic acclimation (CA). A genetic transformation system was developed as a first step to elucidate the molecular mechanism of CA. The results show that Synechococcus sp. CC9311 cells were sensitive to four commonly used antibiotics: ampicillin, kanamycin, spectinomycin, and chloramphenicol. An integrative plasmid to disrupt the putative phycoerythrin lyase gene mpeV, using a kanamycin resistance gene as selectable marker, was constructed by recombinant polymerase chain reaction. The plasmid was then transformed into Synechococcus sp. CC9311 via electroporation. High transformation efficiency was achieved at a field strength of 2 kV/cm. DNA analysis showed that mpeV was fully disrupted following challenge of the transformants with a high concentration of kanamycin. In addition, the transformants that displayed poor growth on agar SN medium could be successfully plated on agarose SN medium. %B Chinese Journal of Oceanology and Limnology %V 31 %P 416–420 %G eng %U https://doi.org/10.1007/s00343-013-2164-5 %R 10.1007/s00343-013-2164-5 %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 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 Environmental Microbiology %D 2011 %T Basin-scale distribution patterns of photosynthetic picoeukaryotes along an Atlantic Meridional Transect %A Kirkham, Amy R %A Jardillier, Ludwig E %A Tiganescu, Ana %A Pearman, John %A Zubkov, Mikhail V %A Scanlan, David J %K Micromonas %K rcc %X Summary Photosynthetic picoeukaryotes (PPEs) of a size ¡ 3 µm play a crucial role in oceanic primary production. However, little is known of the structure of the PPE community over large spatial scales. Here, we investigated the distribution of various PPE classes along an Atlantic Meridional Transect sampled in boreal autumn 2004 that encompasses a range of ocean provinces (gyres, upwelling, temperate regions), using dot blot hybridization technology targeting plastid 16S rRNA gene amplicons. Two algal classes, Prymnesiophyceae and Chrysophyceae, dominated the PPE community throughout the Atlantic Ocean, over a range of water masses presenting different trophic profiles. However, these classes showed strongly complementary distributions with Chrysophyceae dominating northern temperate waters, the southern gyre and equatorial regions, while prymnesiophytes dominated the northern gyre. Phylogenetic analyses using both plastid and nuclear rRNA genes revealed a high diversity among members of both classes, including sequences contained in lineages with no close cultured counterpart. Other PPE classes were less prevalent along the transect, with members of the Cryptophyceae, Pelagophyceae and Eustigmatophyceae essentially restricted to specific regions. Multivariate statistical analyses revealed strong relationships between the distribution patterns of some of these latter PPE classes and temperature, light intensity and nutrient concentrations. Cryptophyceae, for example, were mostly found in the upwelling region and associated with higher nutrient concentrations. However, the key classes of Prymnesiophyceae and Chrysophyceae were not strongly influenced by the variables measured. Although there appeared to be a positive relationship between Chrysophyceae distribution and light intensity, the complementary distributions of these classes could not be explained by the variables recorded and this requires further explanation. %B Environmental Microbiology %V 13 %P 975–990 %G eng %U http://dx.doi.org/10.1111/j.1462-2920.2010.02403.x %R 10.1111/j.1462-2920.2010.02403.x %0 Journal Article %J Biogeosciences %D 2011 %T Diversity of cultivated and metabolically active aerobic anoxygenic phototrophic bacteria along an oligotrophic gradient in the Mediterranean Sea %A Jeanthon, Christian %A Boeuf, Dominique %A Dahan, Océane %A Le Gall, F %A Garczarek, Laurence %A Bendif, El Mahdi %A Lehours, Anne-Catherine %K 2011 %K rcc %K SBR$_\textrmP$hyto$_\textrmD$PO %K SBR$_\textrmP$hyto$_\textrmE$PPO %K SBR$_\textrmP$hyto$_\textrmP$PM %K sbr?hyto$_\textrmd$ipo %K sbr?hyto?app %B Biogeosciences %V 8 %P 1955–1970 %G eng %R 10.5194/bg-8-1955-2011 %0 Journal Article %J Journal of Phycology %D 2011 %T Transcriptome analyses reveal differential gene expression patterns between the life-cycle stages of Emiliania huxleyi (Haptophyta) and reflect specialization to different ecological niches %A Rokitta, Sebastian D %A de Nooijer, Lennart J %A Trimborn, Scarlett %A de Vargas, Colomban %A Rost, Björn %A John, Uwe %K 2011 %K endocytosis %K Life-cycle stages %K microarray %K quantitative RT-PCR %K rcc %K SBR$_\textrmP$hyto$_\textrmE$PPO %K sbr?hyto?ppo %K transcriptome profiling %X Coccolithophores, especially the abundant, cosmopolitan species Emiliania huxleyi (Lohmann) W. W. Hay et H. P. Mohler, are one of the main driving forces of the oceanic carbonate pump and contribute significantly to global carbon cycling, due to their ability to calcify. A recent study indicates that termination of diploid blooms by viral infection induces life-cycle transition, and speculation has arisen about the role of the haploid, noncalcifying stage in coccolithophore ecology. To explore gene expression patterns in both life-cycle stages, haploid and diploid cells of E. huxleyi (RCC 1217 and RCC 1216) were acclimated to limiting and saturating photon flux densities. Transcriptome analyses were performed to assess differential genomic expression related to different ploidy levels and acclimation light intensities. Analyses indicated that life-cycle stages exhibit different properties of regulating genome expression (e.g., pronounced gene activation and gene silencing in the diploid stage), proteome maintenance (e.g., increased turnover of proteins in the haploid stage), as well as metabolic processing (e.g., pronounced primary metabolism and motility in the haploid stage and calcification in the diploid stage). Furthermore, higher abundances of transcripts related to endocytotic and digestive machinery were observed in the diploid stage. A qualitative feeding experiment indicated that both life-cycle stages are capable of particle uptake (0.5 ??m diameter) in late-stationary growth phase. Results showed that the two life-cycle stages represent functionally distinct entities that are evolutionarily shaped to thrive in the environment they typically inhabit. %B Journal of Phycology %V 47 %P 829–838 %G eng %U http://dx.doi.org/10.1111/j.1529-8817.2011.01014.x %R 10.1111/j.1529-8817.2011.01014.x %0 Journal Article %J Journal of Phycology %D 2010 %T Dna Barcoding of Chlorarachniophytes Using Nucleomorph Its Sequences1 %A Gile, Gillian H. %A Stern, Rowena F. %A James, Erick R. %A Keeling, Patrick J. %K Bigelowiella %K Chlorarachnion %K culture collections %K Gymnochlora %K internal transcribed spacer %K Lotharella %K Norrisiella %K Partenskyella %K RCC337 %K RCC375 %K RCC376 %K RCC435 %K RCC530 %K RCC531 %K RCC623 %K RCC626 %X Chlorarachniophytes are a small group of marine photosynthetic protists. They are best known as examples of an intermediate stage of secondary endosymbiosis: their plastids are derived from green algae and retain a highly reduced nucleus, called a nucleomorph, between the inner and outer pairs of membranes. Chlorarachniophytes can be challenging to identify to the species level, due to their small size, complex life cycles, and the fact that even genus-level diagnostic morphological characters are observable only by EM. Few species have been formally described, and many available culture collection strains remain unnamed. To alleviate this difficulty, we have developed a barcoding system for rapid and accurate identification of chlorarachniophyte species in culture, based on the internal transcribed spacer (ITS) region of the nucleomorph rRNA cistron. Although this is a multicopy locus, encoded in both subtelomeric regions of each chromosome, interlocus variability is low due to gene conversion by homologous recombination in this region. Here, we present barcode sequences for 39 cultured strains of chlorarachniophytes (>80% of currently available strains). Based on barcode data, other published molecular data, and information from culture records, we were able to recommend names for 21 out of the 24 unidentified, partially identified, or misidentified chlorarachniophyte strains in culture. Most strains could be assigned to previously described species, but at least two to as many as five new species may be present among cultured strains. %B Journal of Phycology %V 46 %P 743–750 %G eng %U http://onlinelibrary.wiley.com/doi/abs/10.1111/j.1529-8817.2010.00851.x %R 10.1111/j.1529-8817.2010.00851.x %0 Journal Article %J BMC Evolutionary Biology %D 2010 %T A phylogenetic mosaic plastid proteome and unusual plastid-targeting signals in the green-colored dinoflagellate Lepidodinium chlorophorum %A Minge, M A %A Shalchian-Tabrizi, K %A Torresen, O K %A Takishita, K %A Probert, I %A Inagaki, Y %A Klaveness, D %A Jakobsen, K S %K 2010 %K rcc %K SBR$_\textrmP$hyto$_\textrmE$PPO %X Background: Plastid replacements through secondary endosymbioses include massive transfer of genes from the endosymbiont to the host nucleus and require a new targeting system to enable transport of the plastid-targeted proteins across 3-4 plastid membranes. The dinoflagellates are the only eukaryotic lineage that has been shown to have undergone several plastid replacement events, and this group is thus highly relevant for studying the processes involved in plastid evolution. In this study, we analyzed the phylogenetic origin and N-terminal extensions of plastid-targeted proteins from Lepidodinium chlorophorum, a member of the only dinoflagellate genus that harbors a green secondary plastid rather than the red algal-derived, peridinin-containing plastid usually found in photosynthetic dinoflagellates. Results: We sequenced 4,746 randomly picked clones from a L. chlorophorum cDNA library. 22 of the assembled genes were identified as genes encoding proteins functioning in plastids. Some of these were of green algal origin. This confirms that genes have been transferred from the plastid to the host nucleus of L. chlorophorum and indicates that the plastid is fully integrated as an organelle in the host. Other nuclear-encoded plastid-targeted protein genes, however, are clearly not of green algal origin, but have been derived from a number of different algal groups, including dinoflagellates, streptophytes, heterokonts, and red algae. The characteristics of N-terminal plastid-targeting peptides of all of these genes are substantially different from those found in peridinin-containing dinoflagellates and green algae. Conclusions: L. chlorophorum expresses plastid-targeted proteins with a range of different origins, which probably arose through endosymbiotic gene transfer (EGT) and horizontal gene transfer (HGT). The N-terminal extension of the genes is different from the extensions found in green alga and other dinoflagellates (peridinin- and haptophyte plastids). These modifications have likely enabled the mosaic proteome of L. chlorophorum. %B BMC Evolutionary Biology %V 10 %P 191 %G eng %R 10.1186/1471-2148-10-191 %0 Journal Article %J The ISME Journal %D 2010 %T Significant CO2 fixation by small prymnesiophytes in the subtropical and tropical northeast Atlantic Ocean %A Jardillier, Ludwig %A Zubkov, Mikhail V %A Pearman, John %A Scanlan, David J %K Micromonas %K rcc %B The ISME Journal %V 4 %P 1180–1192 %G eng %U http://dx.doi.org/10.1038/ismej.2010.36 http://www.nature.com/ismej/journal/vaop/ncurrent/suppinfo/ismej201036s1.html %R 10.1038/ismej.2010.36 %0 Conference Paper %B Third international barcode of life conference %D 2009 %T DNA barcoding of protists in culture collections %A Meusnier, Isabelle %A Andersen, Robert A %A Stern, Rowena %A Bertrand, C %A Kuepper, Frithjof %A Brand, Jerry %A Friedl, Thomas %A Blackburn, Susan %A Dinh, Donna %A Acreman, Judy %A Sedláček, Ivo %A Přibyl, Pavel %A Jutson, Maria %A Phang, Siew Moi %A Melkonian, M %A Karpov, S %A Hajibabaei, Mehrdad %K ? No DOI found %K rcc %K SBR$_\textrmP$hyto$_\textrmD$PO %B Third international barcode of life conference %C Mexico City %G eng %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 Molecular Biology and Evolution %D 2008 %T Clues about the genetic basis of adaptation emerge from comparing the proteomes of two Ostreococcus ecotypes (Chlorophyta, Prasinophyceae) %A Jancek, S %A Gourbiere, S %A Moreau, H %A Piganeau, G %K adaptation %K Base Composition %K Chlorophyta/*genetics %K Ecosystem %K Physiological/*genetics %K Phytoplankton/genetics %K Proteome/*genetics %K rcc %K Species Specificity %X We compared the proteomes of two picoplanktonic Ostreococcus unicellular green algal ecotypes to analyze the genetic basis of their adaptation with their ecological niches. We first investigated the function of the species-specific genes using Gene Ontology databases and similarity searches. Although most species-specific genes had no known function, we identified several species-specific functions involved in various cellular processes, which could be critical for environmental adaptations. Additionally, we investigated the rate of evolution of orthologous genes and its distribution across chromosomes. We show that faster evolving genes encode significantly more membrane or excreted proteins, consistent with the notion that selection acts on cell surface modifications that is driven by selection for resistance to viruses and grazers, keystone actors of phytoplankton evolution. The relationship between GC content and chromosome length also suggests that both strains have experienced recombination since their divergence and that lack of recombination on the two outlier chromosomes could explain part of their peculiar genomic features, including higher rates of evolution. %B Molecular Biology and Evolution %V 25 %P 2293–2300 %G eng %U http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=18678753 %R 10.1093/molbev/msn168 %0 Journal Article %J Environmental Microbiology %D 2008 %T Ecological niche partitioning in the picoplanktonic green alga Micromonas pusilla: evidence from environmental surveys using phylogenetic probes %A Foulon, E %A Not, F %A Jalabert, F %A Cariou, T %A Massana, R %A Simon, N %K 2008 %K rcc %K SBR$_\textrmP$hyto$_\textrmD$PO %K sbr?hyto$_\textrmd$ipo %B Environmental Microbiology %V 10 %P 2433–2443 %G eng %R 10.1111/j.1462-2920.2008.01673.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 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 PLoS genetics %D 2007 %T Patterns and implications of gene gain and loss in the evolution of Prochlorococcus %A Kettler, G %A Martiny, A C %A Huang, K %A Zucker, J %A Coleman, M L %A Rodrigue, S %A Chen, F %A Lapidus, A %A Ferriera, S %A Johnson, J %A Steglich, C %A Church, G %A Richardson, P %A Chisholm, S W %K rcc %B PLoS genetics %V 3 %P e231 %G eng %R 10.1371/journal.pgen.0030231 %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 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 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