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386 results on '"Bernard, Cécile"'

1. Geochemistry of an endorheic thalassohaline ecosystem: the Dziani Dzaha crater lake (Mayotte Archipelago, Indian Ocean)

Author

Sarazin, Gérard, Jézéquel, Didier, Leboulanger, Christophe, Fouilland, Eric, Le Floc’h, Emilie, Bouvy, Marc, Gérard, Emmanuelle, Agogué, Hélène, Bernard, Cécile, Hugoni, Mylène, Grossi, Vincent, Troussellier, Marc, and Ader, Magali

Subjects
Thalassohaline lake, Endorheic ecosystem, Cyanobacteria, Methane emission, Biogeochemistry, Mayotte, Geophysics. Cosmic physics, QC801-809, Chemistry, QD1-999, Geology, QE1-996.5
Abstract

Dziani Dzaha is a maar the age of which is close to 4000 years. While its water is thought to have originated from seawater it is now considered as an extreme environment due to its hypersaline and alkaline characteristics. Those extreme features have led to the simplification of the trophic network. Cyanobacteria account for up to 95% of the photosynthetic biomass. The main biogeochemical processes, i.e. photosynthesis, bacterial sulfate reduction and methanogenesis could explain the current water composition. As far as we know, this ecosystem could be unique on Earth, extending the nature and chemical limits of aquatic inland ecosystems.

Published
2020
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15. Transcriptomic insights into the dominance of two phototrophs throughout the water column of a tropical hypersaline-alkaline crater lake (Dziani Dzaha, Mayotte).

Author

Duperron, Sébastien, Halary, Sébastien, Bouly, Jean-Pierre, Roussel, Théotime, Hugoni, Myléne, Bruto, Maxime, Oger, Philippe M., Duval, Charlotte, Woo, Anthony, Jézéquel, Didier, Ader, Magali, Leboulanger, Christophe, Agogué, Hélène, Grossi, Vincent, Troussellier, Marc, and Bernard, Cécile

Subjects
CRATER lakes, ANOXIC zones, GENE expression, TRANSCRIPTOMES, DEPTH profiling, COATED vesicles
Abstract

Saline-alkaline lakes often shelter high biomasses despite challenging conditions, owing to the occurrence of highly adapted phototrophs. Dziani Dzaha (Mayotte) is one such lake characterized by the stable co-dominance of the cyanobacterium Limnospira platensis and the picoeukaryote Picocystis salinarum throughout its water column. Despite light penetrating only into the uppermost meter, the prevailing co-dominance of these species persists even in light- and oxygen-deprived zones. Here, a depth profile of phototrophs metatranscriptomes, annotated using genomic data from isolated strains, is employed to identify expression patterns of genes related to carbon processing pathways including photosynthesis, transporters and fermentation. The findings indicate a prominence of gene expression associated with photosynthesis, with a peak of expression around 1 m below the surface, although the light intensity is very low and only red and dark red wavelengths can reach it, given the very high turbidity linked to the high biomass of L. platensis. Experiments on strains confirmed that both species do grow under these wavelengths, at rates comparable to those obtained under white light. A decrease in the expression of photosynthesis-related genes was observed in L. platensis with increasing depth, whereas P. salinarum maintained a very high pool of psbA transcripts down to the deepest point as a possible adaptation against photodamage, in the absence and/or very low levels of expression of genes involved in protection. In the aphotic/anoxic zone, expression of genes involved in fermentation pathways suggests active metabolism of reserve or available dissolved carbon compounds. Overall, L. platensis seems to be adapted to the uppermost water layer, where it is probably maintained thanks to gas vesicles, as evidenced by high expression of the gvpA gene. In contrast, P. salinarum occurs at similar densities throughout the water column, with a peak in abundance and gene expression levels which suggests a better adaptation to lower light intensities. These slight differences may contribute to limited inter-specific competition, favoring stable co-dominance of these two phototrophs. [ABSTRACT FROM AUTHOR]

Published
2024
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16. Phytoplanktonic species in the haloalkaline Lake Dziani Dzaha select their archaeal microbiome

Author

Bruto, Maxime, primary, Oger, Philippe M., additional, Got, Patrice, additional, Bernard, Cécile, additional, Melayah, Delphine, additional, Cloarec, Lilian A., additional, Duval, Charlotte, additional, Escalas, Arthur, additional, Duperron, Sébastien, additional, Guigard, Ludivine, additional, Leboulanger, Christophe, additional, Ader, Magali, additional, Sarazin, Gerard, additional, Jézéquel, Didier, additional, Agogué, Hélène, additional, Troussellier, Marc, additional, and Hugoni, Mylène, additional

Published
2023
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18. Diversity, metabolome profiling and bioactivities of benthic filamentous cyanobacteria isolated from coastal mangroves of Mayotte

Author

Wang, Huibin, primary, Halary, Sébastien, additional, Duval, Charlotte, additional, Bernard, Cécile, additional, Troussellier, Marc, additional, Beniddir, Mehdi A., additional, Brunel, Jean-Michel, additional, Castaldi, Andrea, additional, Caudal, Flore, additional, Golléty, Claire, additional, Martin, Coralie, additional, Bourguet-Kondracki, Marie-Lise, additional, and Duperron, Sébastien, additional

Published
2023
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22. Diversity, metabolome profiling and bioactivities of benthic filamentous cyanobacteria isolated from coastal mangroves of Mayotte

Author

Wang, Huibin, Halary, Sébastien, Duval, Charlotte, Bernard, Cécile, Troussellier, Marc, Beniddir, Mehdi A., Brunel, Jean-michel, Castaldi, Andrea, Caudal, Flore, Golléty, Claire, Martin, Coralie, Bourguet-kondracki, Marie-lise, Duperron, Sebastien, Wang, Huibin, Halary, Sébastien, Duval, Charlotte, Bernard, Cécile, Troussellier, Marc, Beniddir, Mehdi A., Brunel, Jean-michel, Castaldi, Andrea, Caudal, Flore, Golléty, Claire, Martin, Coralie, Bourguet-kondracki, Marie-lise, and Duperron, Sebastien

Abstract

IntroductionCyanobacteria are important members of the dense biofilms that colonize available substrates in mangrove habitats worldwide. However, their taxonomic diversity and biological activities have received little attention. MethodsThe occurrence of cyanobacteria is evaluated in 27 biofilms collected from mangroves in Mayotte. Filamentous cyanobacterial strains were isolated and characterized using 16S rRNA comparative gene sequence analysis. LC-MS/MS experiments were performed on the crude extracts of the faster-growing strains, and construction of their molecular network showed a conspectus of their chemical diversity. Biological activities of the strain extracts were then evaluated using standard assays. Results and discussionIsolation procedures yielded 43 strains representing 22 species-level taxa, of which only three could be assigned to existing species. Some of these strains were among the most abundant cyanobacteria present in biofilms. PCR assays did not support the production of the major cyanotoxins. Analysis of metabolites from 23 strains using both in silico tools ISDB- DNP (In silico Data Base–Dictionary of Natural Products) and MolDiscovery, revealed occurrence of godavarin K, a limonoid natural product previously isolated from the seeds of an Indian mangrove tree. This annotation was further confirmed by the marine database MarinLit, suggesting that cyanobacteria might be an alternative source of godavarin K and its four isomers. While no significant antimicrobial and cytotoxic activities were observed, some strains exhibited anthelmintic and antibiofilm activities that warrant further investigation and may be relevant to biofilm ecology. Mangrove biofilms thus appear to be an untapped reservoir of novel culturable cyanobacterial lineages, with bioactivities relevant to their biofilm lifestyle, which may be of interest for bioinspiration.

Published
2023
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25. Widespread formation of intracellular calcium carbonates by the bloom‐forming cyanobacteriumMicrocystis

Author

Gaëtan, Juliette, primary, Halary, Sébastien, additional, Millet, Maxime, additional, Bernard, Cécile, additional, Duval, Charlotte, additional, Hamlaoui, Sahima, additional, Hecquet, Amandine, additional, Gugger, Muriel, additional, Marie, Benjamin, additional, Mehta, Neha, additional, Moreira, David, additional, Skouri‐Panet, Fériel, additional, Travert, Cynthia, additional, Duprat, Elodie, additional, Leloup, Julie, additional, and Benzerara, Karim, additional

Published
2022
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37. The success of the bloom-forming cyanobacteria Planktothrix: Genotypes variability supports variable responses to light and temperature stress

Author

Kim Tiam, Sandra, primary, Comte, Katia, additional, Dalle, Caroline, additional, Delagrange, Marine, additional, Djediat, Chakib, additional, Ducos, Bertrand, additional, Duval, Charlotte, additional, Feilke, Kathleen, additional, Hamlaoui, Sahima, additional, Le Manach, Séverine, additional, Setif, Pierre, additional, Yéprémian, Claude, additional, Marie, Benjamin, additional, Kirilovsky, Diana, additional, Gugger, Muriel, additional, and Bernard, Cécile, additional

Published
2022
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38. Characterization of Potential Threats from Cyanobacterial Toxins in Lake Victoria Embayments and during Water Treatment

Author

Olokotum, Mark, Humbert, Jean-françois, Quiblier, Catherine, Okello, William, Semyalo, Ronald, Troussellier, Marc, Marie, Benjamin, Baumann, Kathrin, Kurmayer, Rainer, Bernard, Cécile, Olokotum, Mark, Humbert, Jean-françois, Quiblier, Catherine, Okello, William, Semyalo, Ronald, Troussellier, Marc, Marie, Benjamin, Baumann, Kathrin, Kurmayer, Rainer, and Bernard, Cécile

Abstract

Africa’s water needs are often supported by eutrophic waterbodies dominated by cyanobacteria posing health threats to riparian populations from cyanotoxins, and Lake Victoria is no exception. In two embayments of the lake (Murchison Bay and Napoleon Gulf), cyanobacterial surveys were conducted to characterize the dynamics of cyanotoxins in lake water and water treatment plants. Forty-six cyanobacterial taxa were recorded and out of these 14 were considered potentially toxigenic (i.e., from the genera Dolichospermum, Microcystis, Oscillatoria, Pseudanabaena and Raphidiopsis). A higher concentration (ranging from 5-10 µg MC-LR equiv. L-1) of microcystins (MCs) was detected in Murchison Bay compared to Napoleon Gulf, with a declining gradient from the inshore (max. 15 µg MC-LR equiv. L-1) to the open lake. In Murchison Bay, an increase either in Microcystis sp. biovolume and MC was observed over the last two decades. Despite high cell densities of toxigenic Microcystis and high MC concentrations, the water treatment plant in Murchison Bay efficiently removed the cyanobacterial biomass, intracellular and dissolved MC to below the lifetime guideline value for exposure via drinking water (< 1.0 µg MC-LR equiv. L-1). Thus, the potential health threats stem from the consumption of untreated water and recreational activities, along the shores of the lake embayments. MC concentrations were predicted from Microcystis cell numbers regulated by environmental factors such as solar radiation, wind speed in the N-S direction and turbidity. Thus, an early warning through microscopical counting of Microcystis cell numbers is proposed to better manage health risks from toxigenic cyanobacteria in Lake Victoria.

Published
2022
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39. Fish gut-associated bacterial communities in a tropical lagoon (Aghien lagoon, Ivory Coast)

Author

Gallet, Alison, Kouamé Yao, Eric, Foucault, Pierre, Bernard, Cécile, Quiblier, Catherine, Humbert, Jean-françois, Kalpy Coulibaly, Julien, Troussellier, Marc, Marie, Benjamin, Duperron, Sebastien, Gallet, Alison, Kouamé Yao, Eric, Foucault, Pierre, Bernard, Cécile, Quiblier, Catherine, Humbert, Jean-françois, Kalpy Coulibaly, Julien, Troussellier, Marc, Marie, Benjamin, and Duperron, Sebastien

Abstract

Aghien lagoon (Ivory Coast) is a eutrophic freshwater lagoon that harbors high biomasses of phytoplankton. Despite Increasing interest in fish gut microbiomes diversity and functions, little data is currently available regarding wild species from tropical west African lakes. Here, gut-associated bacterial communities are investigated in four fish species that are consumed by locale populations, namely the Cichlidae Hemichromis fasciatus, Tilapia guineensis and Sarotherodon melanotheron, and the Claroteidae Chrysichthys nigrodigitatus. Species-related differences are identified, that can be attributed to host phylogeny and diet. Important variations throughout the year are observed in T. guineensis and C. nigrodigitatus. This result emphasized the importance of time-series sampling and comparison with environmental variables even in tropical regions, that are not often conducted in wild populations. Effects of environmental factors (anthropogenic or not) on the microbiota and potential outcomes for fish health and populations sustainability need to be further explored. Interestingly, fish appear as major reservoirs of bacterial diversity, suggesting that they could contribute to the overall stability and resilience of bacterial communities present in the Aghien lagoon.

Published
2022
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41. Impacts of nutrient loading and fish grazing on the phytoplankton community and cyanotoxin production in a shallow tropical lake: Results from mesocosm experiments

Author

Ahoutou, Mathias K., primary, Yao, Eric Kouamé, additional, Djeha, Rosine Y., additional, Kone, Mamadou, additional, Tambosco, Kevin, additional, Duval, Charlotte, additional, Hamlaoui, Sahima, additional, Bernard, Cécile, additional, Bouvy, Marc, additional, Marie, Benjamin, additional, Montuelle, Bernard, additional, Troussellier, Marc, additional, Konan, Felix K., additional, Coulibaly, Julien Kalpy, additional, Dosso, Mireille, additional, Humbert, Jean‐François, additional, and Quiblier, Catherine, additional

Published
2022
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42. Impacts of nutrient loading and fish grazing on the phytoplankton community and cyanotoxin production in a shallow tropical lake: Results from mesocosm experiments

Author

Ahoutou, Mathias Koffi, primary, Yao, Eric Kouamé, additional, Djeha, Rosine Yao, additional, Kone, Mamadou, additional, Tambosco, Kevin, additional, Duval, Charlotte, additional, Hamlaoui, Sahima, additional, Bernard, Cécile, additional, Bouvy, Marc, additional, Marie, Benjamin, additional, Montuelle, Bernard, additional, Troussellier, Marc, additional, Konan, Felix Koffi, additional, Dosso, Mireille, additional, Humbert, Jean-François, additional, Quiblier, Catherine, additional, and Kalpy, Julien, additional

Published
2022
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44. Dynamics of the Metabolome of Aliinostoc sp. PMC 882.14 in Response to Light and Temperature Variations

Author

Le Moigne, Damien, Demay, Justine, Reinhardt, Anita, Bernard, Cécile, Kim Tiam, Sandra, Marie, Benjamin, Muséum national d'Histoire naturelle (MNHN), Thermes Nationaux Aix Les Bains, Partenaires INRAE, Thermes de Balaruc-les-Bains, Laboratoire d'Ecologie Microbienne - UMR 5557 (LEM), Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Ecole Nationale Vétérinaire de Lyon (ENVL)-VetAgro Sup - Institut national d'enseignement supérieur et de recherche en alimentation, santé animale, sciences agronomiques et de l'environnement (VAS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)

Subjects
secondary metabolite induction, culture conditions, [SDV.BBM]Life Sciences [q-bio]/Biochemistry, Molecular Biology, high-resolution mass spectrometry, cyanobacteria, metabolomics, Microbiology, Article, QR1-502
Abstract

International audience; Cyanobacteria are microorganisms able to adapt to a wide variety of environmental conditions and abiotic stresses. They produce a large number of metabolites that can participate in the dynamic adaptation of cyanobacteria to a range of different light, temperature, and nutrient conditions. Studying the metabolite profile is one way to understand how the physiological status of cells is related to their adaptive response. In this study, we sought to understand how the diversity and dynamics of the whole metabolome depended on the growth phase and various abiotic factors such as light intensity and temperature. The cyanobacterium, Aliinostoc sp. PMC 882.14, was selected for its large number of biosynthetic gene clusters. One group of cells was grown under normal conditions as a control, while other groups were grown under higher light or temperature. Metabolomes were analyzed by mass spectrometry (qTOF-MS/MS) combined with untargeted analysis to investigate metabolite dynamics, and significant variation was found between exponential and stationary phases, regardless of culture conditions. In the higher light group, the synthesis of several metabolites, including shinorine, was induced while other metabolites, such as microviridins, were synthesized under higher temperature conditions. Among highly regulated metabolites, we observed the presence of mycosporine-like amino acids (MAAs) and variants of somamides, microginins, and microviridins. This study demonstrated the importance of considering the physiological state of cyanobacteria for comparative global metabolomics and studies of the regulatory processes involved in production of specific metabolites. Our results also open up new perspectives on the use of organisms such as cyanobacteria for the targeted production of bioactive metabolites.

Published
2021
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45. Widespread formation of intracellular calcium carbonates by the bloom‐forming cyanobacterium Microcystis.

Author

Gaëtan, Juliette, Halary, Sébastien, Millet, Maxime, Bernard, Cécile, Duval, Charlotte, Hamlaoui, Sahima, Hecquet, Amandine, Gugger, Muriel, Marie, Benjamin, Mehta, Neha, Moreira, David, Skouri‐Panet, Fériel, Travert, Cynthia, Duprat, Elodie, Leloup, Julie, and Benzerara, Karim

Subjects
MICROCYSTIS, INTRACELLULAR calcium, CALCIUM carbonate, GEOCHEMICAL cycles, BIOMINERALIZATION, GENOTYPES
Abstract

The formation of intracellular amorphous calcium carbonates (iACC) has been recently observed in a few cultured strains of Microcystis, a potentially toxic bloom‐forming cyanobacterium found worldwide in freshwater ecosystems. If iACC‐forming Microcystis are abundant within blooms, they may represent a significant amount of particulate Ca. Here, we investigate the significance of iACC biomineralization by Microcystis. First, the presence of iACC‐forming Microcystis cells has been detected in several eutrophic lakes, indicating that this phenomenon occurs under environmental conditions. Second, some genotypic (presence/absence of ccyA, a marker gene of iACC biomineralization) and phenotypic (presence/absence of iACC) diversity have been detected within a collection of strains isolated from one single lake. This illustrates that this trait is frequent but also variable within Microcystis even at a single locality. Finally, one‐third of publicly available genomes of Microcystis were shown to contain the ccyA gene, revealing a wide geographic and phylogenetic distribution within the genus. Overall, the present work shows that the formation of iACC by Microcystis is common under environmental conditions. While its biological function remains undetermined, this process should be further considered regarding the biology of Microcystis and implications on the Ca geochemical cycle in freshwater environments. [ABSTRACT FROM AUTHOR]

Published
2023
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48. Strong reorganization of multi-domain microbial networks associated with primary producers sedimentation from oxic to anoxic conditions in an hypersaline lake

Author

Escalas, Arthur, primary, Troussellier, Marc, additional, Melayah, Delphine, additional, Bruto, Maxime, additional, Nicolas, Sébastien, additional, Bernard, Cécile, additional, Ader, Magali, additional, Leboulanger, Christophe, additional, Agogué, Hélène, additional, and Hugoni, Mylène, additional

Published
2021
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49. Influence of aphotic haloclines and euxinia on organic biomarkers and microbial communities in a thalassohaline and alkaline volcanic crater lake

Author

Sala, David, primary, Grossi, Vincent, additional, Agogué, Hélène, additional, Leboulanger, Christophe, additional, Jézéquel, Didier, additional, Sarazin, Gérard, additional, Antheaume, Ingrid, additional, Bernard, Cécile, additional, Ader, Magali, additional, and Hugoni, Mylène, additional

Published
2021
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50. Recherche sur la fin de vie, la nécessité d’un consensus : premiers résultats

Author

Bernard, Cécile, primary, Hamidou, Zeinab, additional, Billa, Oumar, additional, Dany, Lionel, additional, Amouroux-Gorsse, Valérie, additional, Dubois, Lise, additional, Gallois, Marion, additional, de Larivière, Emmanuel, additional, Lamie, Séverine, additional, Peyrat-Apicella, Delphine, additional, Vezy, Pierre, additional, Aubry, Régis, additional, Guillemin, Francis, additional, Dabakuyo-Yonli, Sandrine, additional, and Auquier, Pascal, additional

Published
2021
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