Didier Jézéquel

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The atmospheric concentration of methane (CH(4)), a major greenhouse gas, is mainly controlled by the activities of methane-producing (methanogens) and methane-consuming (methanotrophs) microorganisms. Freshwater lakes are identified as one of the main CH(4) sources, as it was estimated that they contribute to 6-16% of natural CH(4) emissions. It is(More)
As for lineages of known methanogens, several lineages of uncultured archaea were recurrently retrieved in freshwater sediments. However, knowledge is missing about how these lineages might be affected and structured according to depth. In the present study, the vertical changes of archaeal communities were characterized in the deep sediment of the(More)
Lake Pavin is a meromictic crater lake located in the French Massif Central area. In this ecosystem, most methane (CH(4)) produced in high quantity in the anoxic bottom layers, and especially in sediments, is consumed in the water column, with only a small fraction of annual production reaching the atmosphere. This study assessed the diversity of(More)
Geochemical researches at Lake Pavin, a low-sulfate-containing freshwater lake, suggest that the dominant biogeochemical processes are iron and sulfate reduction, and methanogenesis. Although the sulfur cycle is one of the main active element cycles in this lake, little is known about the sulfate-reducer and sulfur-oxidizing bacteria. The aim of this study(More)
An annual survey of the chemical composition both in dissolved and particulate phases of a eutrophic lake was performed from September 1995 to October 1996. All major elements and many trace elements were analyzed in the tributary and in the water column. Element fluxes were determined via sediment traps. Several sediment cores and interstitial water(More)
As biominerals are good tracers of microbial interactions with the environment, they may provide signatures of microbial evolution and paleoenvironmental conditions. Since modern analogues of past environments help with defining proxies and biosignatures, we explored microbe mineral interactions in the water column of a maar lake, located in France: Lake(More)
Corynebacterium glutamicum is used for the industrial production of glutamate. Excretion of the amino acid may be induced by various means. We have analyzed the characteristics of glutamate excretion induced by two amine surfactants, dodecylammonium acetate (DA) and dodecyltrimethylammonium bromide (DTA). Addition of these surfactants induced an immediate(More)
We present here an improved and reliable method for measuring the concentration of dissolved inorganic carbon (DIC) and its isotope composition (delta(13)C(DIC)) in natural water samples. Our apparatus, a gas chromatograph coupled to an isotope ratio mass spectrometer (GCIRMS), runs in a quasi-automated mode and is able to analyze about 50 water samples per(More)
About 80% and more than 90% of the dissolved organic carbon (DOC) in the bottom water of Lake Pavin were isolated, respectively, on Amberlite XAD and Spherodex DEAE resins. Trace element concentrations in the fractions isolated were analyzed by using ICP-MS. Uranium, molybdenum, and antimony were found to be about 40% associated with fulvic and hydrophilic(More)
Identi¢cationofmicrobial communities involved in themethane cycle ofa freshwatermeromictic lake Corinne Biderre-Petit, Didier Jézéquel, Eric Dugat-Bony, Filipa Lopes, Jan Kuever, Guillaume Borrel, Eirc Viollier, Gerard Fonty & Pierre Peyret Laboratoire Microorganismes: Génome et Environnement, Clermont Université, Université Blaise Pascal, BP 10448,(More)