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Auteur Gounand, I.; Daufresne, T.; Gravel, D.; Bouvier, C.; Bouvier, T.; Combe, M.; Gougat-Barbera, C.; Poly, F.; Torres-Barcelo, C.; Mouquet, N.
Titre Size evolution in microorganisms masks trade-offs predicted by the growth rate hypothesis Type Article scientifique
Année 2016 Publication Revue Abrégée Proc. R. Soc. B-Biol. Sci.
Volume 283 Numéro 1845 Pages 20162272
Mots-Clés Bacteria; bacterial community; biological stoichiometry; cell-size; escherichia-coli; experimental evolution; fresh-water; growth rate hypothesis; inorganic polyphosphate; intrinsic growth; mechanistic approach; Pseudomonas fluorescens; resource competition; r/K strategies; Stoichiometry; variable environment
Résumé Adaptation to local resource availability depends on responses in growth rate and nutrient acquisition. The growth rate hypothesis (GRH) suggests that growing fast should impair competitive abilities for phosphorus and nitrogen due to high demand for biosynthesis. However, in microorganisms, size influences both growth and uptake rates, which may mask trade-offs and instead generate a positive relationship between these traits (size hypothesis, SH). Here, we evolved a gradient of maximum growth rate (mu(max)) from a single bacterium ancestor to test the relationship among mu(max), competitive ability for nutrients and cell size, while controlling for evolutionary history. We found a strong positive correlation between mu(max) and competitive ability for phosphorus, associated with a trade-off between mu(max) and cell size: strains selected for high mu(max) were smaller and better competitors for phosphorus. Our results strongly support the SH, while the trade-offs expected under GRH were not apparent. Beyond plasticity, unicellular populations can respond rapidly to selection pressure through joint evolution of their size and maximum growth rate. Our study stresses that physiological links between these traits tightly shape the evolution of competitive strategies.
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ISSN 0962-8452 ISBN Médium
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Numéro d'Appel MARBEC @ alain.herve @ collection 2055
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Auteur Galès, A.; Bonnafous, A.; Carré, C.; Jauzein, V.; Lanouguère, E.; Le Floc'h, E.; Pinoit, J.; Poullain, C.; Roques, C.; Sialve, B.; Simier, M.; Steyer, J.-P.; Fouilland, E.
Titre Importance of ecological interactions during wastewater treatment using High Rate Algal Ponds under different temperate climates Type Article scientifique
Année 2019 Publication Revue Abrégée Algal Research
Volume 40 Numéro Pages 101508
Mots-Clés Ammonia and phosphate removal; Bacteria; Microalgae; Predators; Urban effluents
Résumé Several studies focused on wastewater treatment in High Rate Algal Ponds (HRAP) suggest that highly variable climatic conditions cause large variations of microalgal biomass productivity. In the present study, we show that similar carbon, nitrogen and phosphorus removal efficiencies were reached in different HRAPs treating urban wastewaters located in two different temperate (Mediterranean and oceanic) climates. Furthermore, similar ecological successions were observed in these HRAPs. During the start-up phase, the consumption of organic matter by detritivores, already present in the wastewater, appears to be necessary for the microalgae to grow within two weeks in spring. The growth of the rapid-growing species, Chlorella sp., followed by the grazing-resilient species, Scenedesmus sp., combined with nitrifying and denitrifying bacterial activity, removed most the ammonia. The resulting exhaustion of ammonia would limit the complete removal of dissolved COD by bacteria and phosphate by microalgae in the HRAPs. This study shows that similar biological and environmental constraints were applied on the HRAPs, making the process efficiency highly reproducible under different temperate latitudes.
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Volume de collection Numéro de collection Edition
ISSN 2211-9264 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2572
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Auteur Gros, O.; Elisabeth, N.H.; Gustave, S.D.D.; Caro, A.; Dubilier, N.
Titre Plasticity of symbiont acquisition throughout the life cycle of the shallow-water tropical lucinid Codakia orbiculata (Mollusca: Bivalvia) Type Article scientifique
Année 2012 Publication Revue Abrégée Environ. Microbiol.
Volume 14 Numéro 6 Pages 1584-1595
Mots-Clés bacteria; bathymodiolus-azoricus; cold; endosymbiont transmission; gill-endosymbionts; identification; in-situ hybridization; population; seeps; sulfur; vertical transmission
Résumé In marine invertebrates that acquire their symbionts from the environment, these are generally only taken up during early developmental stages. In the symbiosis between lucinid clams and their intracellular sulfur-oxidizing bacteria, it has been shown that the juveniles acquire their symbionts from an environmental stock of free-living symbiont forms, but it is not known if adult clams are still competent to take up symbiotic bacteria from the environment. In this study, we investigated symbiont acquisition in adult specimens of the lucinid clam Codakia orbiculata, using transmission electron microscopy, fluorescence in situ hybridization, immunohistochemistry and PCR. We show here that adults that had no detectable symbionts after starvation in aquaria for 6 months, rapidly reacquired symbionts within days after being returned to their natural environments in the field. Control specimens that were starved and then exposed to seawater aquaria with sulfide did not reacquire symbionts. This indicates that the reacquisition of symbionts in the starved clams returned to the field was not caused by high division rates of a small pool of remaining symbionts that we were not able to detect with the methods used here. Immunohistochemistry with an antibody against actin, a protein involved in the phagocytosis of intracellular bacteria, showed that actin was expressed at the apical ends of the gill cells that took up symbionts, providing further evidence that the symbionts were acquired from the environment. Interestingly, actin expression was also observed in symbiont-containing cells of untreated lucinids freshly collected from the environment, indicating that symbiont acquisition from the environment occurs continuously in these clams throughout their lifetime.
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Langue English Langue du Résumé Titre Original
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Volume de collection Numéro de collection Edition
ISSN 1462-2912 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 784
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Auteur Auguet, J.C.; Montanie, H.; Delmas, D.; Hartmann, H.J.; Huet, V.
Titre Dynamic of virioplankton abundance and its environmental control in the Charente estuary (France) Type Article scientifique
Année 2005 Publication Revue Abrégée Microb Ecol
Volume 50 Numéro 3 Pages 337-349
Mots-Clés Bacteria/isolation & purification Ecosystem *Environment; Controlled France Plankton/*isolation & purification Rivers/chemistry/*microbiology Seasons Viruses/*isolation & purification Water Microbiology
Résumé The Charente River provides nutrient- and virus-rich freshwater input to the Marennes Oleron Basin, the largest oyster-producing region in Europe. To evaluate virioplankton distribution in the Charente Estuary and identify which environmental variables control dynamic of virioplankton abundance, five stations defined by a salinity gradient (0-0.5, 0.6-5, 13-17, 20-24, and higher than 30 PSU) were surveyed over a year. Viral abundance was related to bacterioplankton abundance and activities, photosynthetic pigments, nutrient concentration, and physical parameters (temperature and salinity). On a spatial scale, virus displayed a decreasing pattern seaward with abundance ranging over the sampling period from 1.4x10(7) to 20.8x10(7) viruses mL-1 making virioplankton the most abundant component of planktonic microorganisms in the Charente Estuary. A good correlation was found between viral and bacterial abundance (rs=0.85). Furthermore, bacterial abundance was the most important predictor of viral abundance explaining alone between 66% (winter) and 76% (summer) of viral variability. However, no relation existed between viral abundance and chlorophyll a. Temporal variations in viral distributions were mainly controlled by temperature through the control of bacterial dynamics. Spatial variations of viral abundance were influenced by hydrodynamic conditions especially during the winter season where virioplankton distribution was entirely driven by mixing processes.
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1296
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Auteur Brouwer, G.M.; Duijnstee, I. a. P.; Hazeleger, J.H.; Rossi, F.; Lourens, L.J.; Middelburg, J.J.; Wolthers, M.
Titre Diet shifts and population dynamics of estuarine foraminifera during ecosystem recovery after experimentally induced hypoxia crises Type Article scientifique
Année 2016 Publication Revue Abrégée Estuar. Coast. Shelf Sci.
Volume 170 Numéro Pages 20-33
Mots-Clés Bacteria; Benthic foraminifera; C-13 label; communities; Diet shifts; differential response; diversity; Hypoxia; in-situ; Intertidal; Macrofauna; Meiofauna; microphytobenthos carbon; population dynamics; Sediment
Résumé This study shows foraminiferal dynamics after experimentally induced hypoxia within the wider context of ecosystem recovery. C-13-labeled bicarbonate and glucose were added to the sediments to examine foraminiferal diet shifts during ecosystem recovery and test-size measurements were used to deduce population dynamics. Hypoxia-treated and undisturbed patches were compared to distinguish natural (seasonal) fluctuations from hypoxia-induced responses. The effect of timing of disturbance and duration of recovery were investigated. The foraminiferal diets and population dynamics showed higher fluctuations in the recovering patches compared to the controls. The foraminiferal diet and population structure of Haynesina germanica and Ammonia beccarii responded differentially and generally inversely to progressive stages of ecosystem recovery. Tracer inferred diet estimates in April and June and the two distinctly visible cohorts in the test-size distribution, discussed to reflect reproduction in June, strongly suggest that the ample availability of diatoms during the first month of ecosystem recovery after the winter hypoxia was likely profitable to A. beccarii. Enhanced reproduction itself was strongly linked to the subsequent dietary shift to bacteria. The distribution of the test dimensions of H. germanica indicated that this species had less fluctuation in population structure during ecosystem recovery but possibly reproduced in response to the induced winter hypoxia. Bacteria seemed to consistently contribute more to the diet of H. germanica than diatoms. For the diet and test-size distribution of both species, the timing of disturbance seemed to have a higher impact than the duration of the subsequent recovery period. (C) 2016 Published by Elsevier Ltd.
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Langue English Langue du Résumé Titre Original
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Volume de collection Numéro de collection Edition
ISSN 0272-7714 ISBN Médium
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Numéro d'Appel MARBEC @ alain.herve @ collection 2065
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