Adaptation des communautés microbienne planctoniques et adhérées dans un système bioélectrochimique

International audienceBioelectrochemical systems (BES) as microbial fuel cells take advantages of microorganisms to convert the chemical energy of organic waste including wastewaters and lignocellulosic biomass into electricity or hydrogen/chemical products. Recently, the discovering that BES can also be harness for product synthesis via microbial electrosynthesis (MES) has greatly expanded the horizon for these systems. MES is a promising strategy which consists in the direct powering of microbial activity with electricity to catalyze conversion of carbon dioxide to transportation fuels and other organic commodities. However, the MES concept is only few years old and scientific data about the functioning and the structure of microbial communities involved are required. In this context, we focused here on the study of communities developed in a BES system. For that, we constructed a dedicated system composed of dual-chamber reactor separated by an anion-exchange membrane and inoculated with biological sludges. Cathode potential was poised at -0.65 volts versus saturated calomel electrode (SCE). Chronoamperometry and cyclic voltammetry experiments were carried out with a multi-channel potentiostat in order to monitor electric activity of the microbial communities. Dynamics of population were achieved by ARISA during experiment and community diversity was investigated at specific time point of interest by sequencing 16S rDNA in bulk phases and in biofilm on the electrodes. Biofilm structures were also visualized using confocal microscopy. Chemical analyses were performed to highlight the metabolic pathways involved. Results showed that current reached intensity of 100 mA/ m². ARISA diversity profiles evolved during the experiment duration showing an adaptation of microbial communities. Pyrosequencing of the 16S rDNA genes revealed specific diversity profiles on the electrodes compared to the bulk. In particular, we observed that Dechloromonas sp. constitute de dominant species (~28% of the total diversity) at the anode whereas this species did not reach more than 1.5% in the bulk and at the cathode. The link between current production, chemical molecules and microbial species diversity is thus discussed. In conclusion, this contribution provides data on the structure and composition of electroactive communities which are crucial for the understanding, the development and the optimization of BES systems

The sheep estrogen receptor : cloning and regulation of expression in the hypothalamo-pituitary axis

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Size heterogeneity of affinity-labeled estrogen receptor in the ram hypothalamo-pituitary axis

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Existence de deux formes distinctes de récepteur GnRH-R chez les poissons téléostéens

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Estrogen receptor protein and mRNA expression in the ovary of sheep

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Estrogen receptor protein and mRNA expression in the ovary of sheep

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Biodégradation du Penta- et 2,4,6-tri-chlorophenol durant la digestion anaérobie des déchets non dangereux

International audienceIn this study isotopic tracing using C-13 labelled pentachlorophenol (PCP) and 2,4,6-trichlorophenol (2,4,6-TCP) is proposed as a tool to distinguish the loss of PCP and 2,4,6-TCP due to biodegradation from other physical processes. This isotopic approach was applied to accurately assess in situ PCP and 2,4,6-TCP degradation under methanogenic conditions in several microcosms made up of household waste. These microcosms were incubated in anaerobic conditions at 35 degrees C (mesophilic) and 55 degrees C (thermophilic) without agitation. The volume of biogas produced (CH4 and CO2), was followed for a period of 130 days. At this stage of stable methanogenesis, C-13(6)-PCP and C-13(6)-2,4,6-TCP were introduced anaerobically in microcosms and its monitoring at mesophilic and thermophilic conditions was performed in parallel by gas chromatography mass spectrometry (GC-MS) and gas chromatography isotope-ratio mass spectrometry (GC-IRMS). This study proved the almost total dechlorination of bioavailable PCP and 2,4,6-TCP into 4-CP at 35 degrees C. Nevertheless, high rate adsorption in particular materials of the two compounds was observed. Furthermore, Carbon-13 Nuclear Magnetic Resonance (C-13-NMR) Spectroscopy analysis of C-13 labelled 2,4,6-TCP mesophilic incubations showed the partial mineralization of 4-CP at 35 degrees C to acetate and then to HCO3-. Consequently, NMR results confirm the biogas isotopic results indicating the mineralization of C-13 labelled 2,4,6-TCP into C-13 (CH4 and CO2). Concerning C-13 labelled PCP mesophilic incubations, the isotopic composition of the biogas still natural until the day 262. In contrast, no de chlorination was observed at 55 degrees C. Thus PCP and 2,4,6-TCP were persistent in thermophilic conditions

Identification of the blood group Lewis(a) determinant in the oviducal mucins of Xenopus tropicalis.

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Stable isotope probing of acetate fed anaerobic batch incubations shows a partial resistance of acetoclastic methanogenesis catalyzed by Methanosarcina to sudden increase of ammonia level

ISI Document Delivery No.: CB3BQHao, Liping Lue, Fan Mazeas, Laurent Quemener, Elie Desmond-Le Madigou, Celine Guenne, Angeline Shao, Liming Bouchez, Theodore He, PinjingAmmonia inhibition represents a major operational issue for anaerobic digestion. In order to refine our understanding of the terminal catabolic steps in thermophilic anaerobic digestion under ammonia stress, we studied batch thermophilic acetate fed experiments at low (0.26 g L-1) and high (7.00 g L-1) Total Ammonia Nitrogen concentrations (TAN). Although methane production started immediately for all incubations and resulted in methane yields close to stoichiometric expectations, a 62-72% decrease of methanogenic rate was observed throughout the incubation at 7.00 g L-1 of TAN compared to 0.26 g L-1. Stable Isotope Probing analysis of active microbial communities in C-13-acetate fed experiments coupled to automated ribosomal intergenic spacer analysis and 16S rDNA pyrotag sequencing confirmed that microbial communities were similar for both TAN conditions. At both TAN levels, the C-13-labeled bacterial community was mainly affiliated to Clostridia-relatives, with OPB54 bacteria being the most abundant sequence in the heavy DNA 16S rDNA pyrotag library. Sequences closely related to Methanosarcina thermophila were also abundantly retrieved in the heavy DNA fractions, showing that this methanogen was still actively assimilating labeled carbon from acetate at free ammonia nitrogen concentrations up to 916 mg L-1. Stable isotopic signature analysis of biogas, measured in unlabele