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Auteur Ben Ouada, S.; Ben Ali, R.; Cimetiere, N.; Leboulanger, C.; Ben Ouada, H.; Sayadi, S.
Titre Biodegradation of diclofenac by two green microalgae: Picocystis sp. and Graesiella sp Type Article scientifique
Année 2019 Publication Revue Abrégée Ecotox. Environ. Safe.
Volume 186 Numéro Pages Unsp-109769
Mots-Clés algae; Biodegradation; Biotransformation; bisphenol-a; contaminants; cyanobacteria; Diclofenac; Extremophiles; light-intensity; Microalgae; pharmaceuticals diclofenac; removal; Removal; temperature; transformation products
Résumé The aim of the present study was to provide an integrated view of algal removal of diclofenac (DCF). Two isolated microalgal strains Picocystis sp. and Graesiella sp. were cultivated under different DCF concentrations and their growth, photosynthetic activity and diclofenac removal efficiency were monitored. Results showed that DCF had slight inhibitory effects on the microalgal growth which did not exceed 21% for Picocystis and 36% for Graesiella after 5 days. Both species showed different patterns in terms of removal efficiency. In presence of Picocystis sp., the amounts of removed DCF were up to 73%, 43% and 25% of 25, 50 and 100 mg L-1 respectively; whereas only 52%, 28% and 24% were removed in the presence of Graesiella at same DCF tested concentrations. DCF removal was insured mainly by biodegradation. To better reveal the mechanism involved, metabolites analyses were performed. Two DCF biodegradation/biotransformation products were detected in presence of Picocystis. This study indicated that Picocystis performed a satisfactory growth capacity and DCF removal efficiency and thus could be used for treatment of DCF contaminated aqueous systems.
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Langue English Langue du Résumé Titre Original
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ISSN 0147-6513 ISBN Médium
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Notes WOS:000496901100040 Approuvé pas de
Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2657
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Auteur Bernard, C.; Escalas, A.; Villeriot, N.; Agogué, H.; Hugoni, M.; Duval, C.; Carré, C.; Got, P.; Sarazin, G.; Jézéquel, D.; Leboulanger, C.; Grossi, V.; Ader, M.; Troussellier, M.
Titre Very Low Phytoplankton Diversity in a Tropical Saline-Alkaline Lake, with Co-dominance of Arthrospira fusiformis (Cyanobacteria) and Picocystis salinarum (Chlorophyta) Type Article scientifique
Année 2019 Publication Revue Abrégée Microb Ecol
Volume 78 Numéro 3 Pages 603-617
Mots-Clés Cyanobacteria; Diversity; Extreme environment; Phytoplankton; Picoeukaryote; Thalassohaline lake
Résumé Lake Dziani Dzaha (Mayotte Island, Indian Ocean) is a tropical thalassohaline lake which geochemical and biological conditions make it a unique aquatic ecosystem considered as a modern analogue of Precambrian environments. In the present study, we focused on the diversity of phytoplanktonic communities, which produce very high and stable biomass (mean2014–2015 = 652 ± 179 μg chlorophyll a L−1). As predicted by classical community ecology paradigms, and as observed in similar environments, a single species is expected to dominate the phytoplanktonic communities. To test this hypothesis, we sampled water column in the deepest part of the lake (18 m) during rainy and dry seasons for two consecutive years. Phytoplanktonic communities were characterized using a combination of metagenomic, microscopy-based and flow cytometry approaches, and we used statistical modeling to identify the environmental factors determining the abundance of dominant organisms. As hypothesized, the overall diversity of the phytoplanktonic communities was very low (15 OTUs), but we observed a co-dominance of two, and not only one, OTUs, viz., Arthrospira fusiformis (Cyanobacteria) and Picocystis salinarum (Chlorophyta). We observed a decrease in the abundance of these co-dominant taxa along the depth profile and identified the adverse environmental factors driving this decline. The functional traits measured on isolated strains of these two taxa (i.e., size, pigment composition, and concentration) are then compared and discussed to explain their capacity to cope with the extreme environmental conditions encountered in the aphotic, anoxic, and sulfidic layers of the water column of Lake Dziani Dzaha.
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Volume de collection Numéro de collection Edition
ISSN 1432-184x ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2494
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Auteur Brauer, V.S.; Stomp, M.; Bouvier, T.; Fouilland, E.; Leboulanger, C.; Confurius-Guns, V.; Weissing, F.J.; Stal, L.J.; Huisman, J.
Titre Competition and facilitation between the marine nitrogen-fixing cyanobacteriunn Cyanothece and its associated bacterial community Type Article scientifique
Année 2015 Publication Frontiers in Microbiology Revue Abrégée
Volume 5 Numéro Pages
Mots-Clés aerobic anoxygenic phototrophs; cyanobacteria; heterotrophic bacteria; microbiota; nitrogen fixation; Phytoplankton; resource competition; species interactions
Résumé N-2-fixing cyanobacteria represent a major source of new nitrogen and carbon for marine microbial communities, but little is known about their ecological interactions with associated microbiota. In this study we investigated the interactions between the unicellular N-2-fixing cyanobacterium Cyanothece sp. Miami BG043511 and its associated free-living chemotrophic bacteria at different concentrations of nitrate and dissolved organic carbon and different temperatures. High temperature strongly stimulated the growth of Cyanothece, but had less effect on the growth and community composition of the chemotrophic bacteria. Conversely, nitrate and carbon addition did not significantly increase the abundance of Cyanothece, but strongly affected the abundance and species composition of the associated chemotrophic bacteria. In nitrate-free medium the associated bacterial community was co-dominated by the putative diazotroph Mesorhizobium and the putative aerobic anoxygenic phototroph Erythrobacter and after addition of organic carbon also by the Flavobacterium Muricauda. Addition of nitrate shifted the composition toward co-dominance by Erythrobacter and the Gammaproteobacterium Marinobacter. Our results indicate that Cyanothece modified the species composition of its associated bacteria through a combination of competition and facilitation. Furthermore, within the bacterial community, niche differentiation appeared to play an important role, contributing to the coexistence of a variety of different functional groups. An important implication of these findings is that changes in nitrogen and carbon availability due to, e.g., eutrophication and climate change are likely to have a major impact on the species composition of the bacterial community associated with N-2-fixing cyanobacteria.
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1101
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Auteur Brauer, V.S.; Stomp, M.; Rosso, C.; van Beusekom, S.A.M.; Emmerich, B.; Stal, L.J.; Huisman, J.
Titre Low temperature delays timing and enhances the cost of nitrogen fixation in the unicellular cyanobacterium Cyanothece Type Article scientifique
Année 2013 Publication Revue Abrégée The ISME journal
Volume 7 Numéro 11 Pages 2105-2115
Mots-Clés climate change; day-night cycle; nitrogen fixation; nitrogenase; respiration; unicellular cyanobacteria
Résumé Marine nitrogen-fixing cyanobacteria are largely confined to the tropical and subtropical ocean. It has been argued that their global biogeographical distribution reflects the physiologically feasible temperature range at which they can perform nitrogen fixation. In this study we refine this line of argumentation for the globally important group of unicellular diazotrophic cyanobacteria, and pose the following two hypotheses: (i) nitrogen fixation is limited by nitrogenase activity at low temperature and by oxygen diffusion at high temperature, which is manifested by a shift from strong to weak temperature dependence of nitrogenase activity, and (ii) high respiration rates are required to maintain very low levels of oxygen for nitrogenase, which results in enhanced respiratory cost per molecule of fixed nitrogen at low temperature. We tested these hypotheses in laboratory experiments with the unicellular cyanobacterium Cyanothece sp. BG043511. In line with the first hypothesis, the specific growth rate increased strongly with temperature from 18 to 30 degrees C, but leveled off at higher temperature under nitrogen-fixing conditions. As predicted by the second hypothesis, the respiratory cost of nitrogen fixation and also the cellular C:N ratio rose sharply at temperatures below 21 degrees C. In addition, we found that low temperature caused a strong delay in the onset of the nocturnal nitrogenase activity, which shortened the remaining nighttime available for nitrogen fixation. Together, these results point at a lower temperature limit for unicellular nitrogen-fixing cyanobacteria, which offers an explanation for their (sub)tropical distribution and suggests expansion of their biogeographical range by global warming.
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Éditeur de collection Titre de collection Titre de collection Abrégé
Volume de collection Numéro de collection Edition
ISSN 1751-7370 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 696
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Auteur Denis, M.; Thyssen, M.; Martin, V.; Manca, B.; Vidussi, F.
Titre Ultraphytoplankton basin-scale distribution in the eastern Mediterranean Sea in winter: link to hydrodynamism and nutrients Type Article scientifique
Année 2010 Publication Revue Abrégée Biogeosciences
Volume 7 Numéro 7 Pages 2227-2244
Mots-Clés adriatic sea; community; cyanobacteria; general-circulation; nifh genes; phosphorus limitation; phytoplankton; pigment distribution; primary productivity; structure; unicellular; warm-core eddy
Résumé The basin-scale distribution of ultraphytoplankton (< 10 mu m) was determined in the upper 200 m of the eastern Mediterranean Sea during the winter season. Four clusters were resolved by flow cytometry on the basis of their optical properties and identified as Synechococcus, Prochlorococcus, pico- (< 3 mu m) and nanoeukaryotes (3-10 mu m). Synechococcus was the most abundant population (maximum abundance of about 37 000 cells cm(-3)) and contributed up to 67.7% to the overall ultraphytoplanktonic carbon biomass, whereas the contribution of Prochlorococcus never exceeded 6.5%. The maximum integrated carbon biomass was 1763, 453, 58 and 571 mg C m(-2) for nanoeukaryotes, picoeukaryotes, Prochlorococcus and Synechococcus respectively. Water mass properties were analyzed on the basis of temperature and salinity distributions in order to account for the general circulation and locate the main hydrodynamic structures (fronts, gyres, transition between western and eastern basins). The effect of the main hydrodynamic structures and nutrients on the ultraphytoplankton distribution was investigated. No positive correlation between nutrients and phytoplankton could be established when considering large scales. However, below 50 m depth, nutrient ratios between particular stations were correlated to corresponding density ratios. In contrast, significant relationships were found between Synechococcus abundance and density, resulting from the impact of a gyre in southern Adriatic basin and a thermohaline front in the Ionian basin. A significant relationship was also found between picoeukaryotes and salinity in the comparison of western and eastern Mediterranean Sea.
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Langue English Langue du Résumé Titre Original
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Volume de collection Numéro de collection Edition
ISSN 1726-4170 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 914
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