Coupled abiotic and biotic sulfurization processes during microbial sulfate reduction with alkyl substrates

International audienc

La nécrophagie comme moyen de survie microbienne dans les fonds de la Mer Morte

International audienc

Bacterial recycling of archaeal biomass as a new strategy for extreme life in Dead Sea deep sediments

Archaea and Bacteria that inhabit the deep subsurface (known as the deep biosphere) play a prevalent role in the recycling of sedimentary organic carbon. In such extreme environment, this process can occur over millions of years (Lomstein et al., 2012) and requires microbial communities to cope with limited sources of energy. Because of this scarcity, metabolic processes come at a high energetic cost, but the ways heterotrophic microbial communities develop to minimize energy expenses for a maximized yield remain unclear. Here, we report molecular biomarker evidence for the recycling of archaeal cell wall constituents by Bacteria in extreme evaporitic facies of Dead Sea deep sediments. Wax esters (WE) derived from the recombination of hydrolyzed products of archaeal membrane lipids were observed in gypsum and/or halite sedimentary deposits down to 243 meters below the lake floor (mblf), implying the reutilization of archaeal necromass by deep subsurface Bacteria. By recycling the building blocks of putatively better adapted Archaea, heterotrophic Bacteria build up intracellular carbon stocks and gain access to free water in this deprived environment. This mechanism illustrates a new pathway of carbon transformation in the subsurface and reveals how life is maintained in extreme environments characterized by long-term isolation and minimal energetic resources

Coupled abiotic and biotic sulfurization processes during microbial sulfate reduction with alkyl substrates

International audienc

Recycling of archaeal biomass as a new strategy for extreme life in Dead Sea deep sediments

Archaea and Bacteria that inhabit the deep subsurface (known as the deep biosphere) play a prevalent role in the recycling of sedimentary organic carbon. In such environments, this process can occur over millions of years and requires microbial communities to cope with extremely limited sources of energy. Because of this scarcity, metabolic processes come at a high energetic cost, but the ways heterotrophic microbial communities develop to minimize energy expenses for a maximized yield remain unclear. Here, we report molecular biomarker evidence for the recycling of archaeal cell wall constituents in extreme evaporitic facies of Dead Sea deep sediments. Wax esters derived from the recombination of hydrolyzed products of archaeal membrane lipids were observed in gypsum and/or halite sedimentary deposits down to 243 m below the lake floor, implying the reutilization of archaeal necromass possibly by deep subsurface bacteria. By recycling the building blocks of putatively better-adapted archaea, heterotrophic bacteria may build up intracellular carbon stocks and mitigate osmotic stress in this energy-deprived environment. This mechanism illustrates a new pathway of carbon transformation in the subsurface and demonstrates how life can be maintained in extreme environments characterized by long-term isolation and minimal energetic resources

La nécrophagie comme moyen de survie microbienne dans les fonds de la Mer Morte

International audienc

Determination of the natural abundance delta N-15 of taurine by gas chromatography-isotope ratio measurement mass spectrometry

The measurement of the nitrogen isotope ratio of taurine (2-aminoethanesulphonic acid) in biological samples has a large number of potential applications. Taurine is a small water-soluble molecule which is notoriously difficult to analyze due to its polarity and functionality. A method is described which allows the determination of the natural abundance delta N-15 values of taurine and structural analogues, such as 3-amino-1-propanesulphonic acid (APSA), by isotope ratio mass spectrometry interfaced to gas chromatography (GC-irm-MS). The one-step protocol exploits the simultaneous derivatization of both functionalities of these aminosulphonic acids by reaction with triethylortho-acetate (TEOA). Conditions have been established which ensure quantitative reaction thus avoiding any nitrogen isotope fractionation during derivatization and workup. The differences in the delta N-15 values of derivatized and non-derivatized taurine and APSA all fall within the working range of 0.4 parts per thousand (-0.02 to 0.39 parts per thousand). When applied to four sources of taurine with various delta N-15 values, the method achieved excellent reproducibility and accuracy. The optimized method enables the determination of the natural abundance delta N-15 values of taurine over the concentration range 1.5-7.84 mu mol.mL(-1) in samples of biological origin. Copyright (C) 2010 John Wiley & Sons, Ltd

Bacterial recycling of archaeal biomass as a new strategy for extreme life in the Dead Sea deep sediment

International audienceSubsurface environments are challenging to life sustainment as they often lack the elements necessary for biological development. The heterotrophic microbial communities commonly inhabiting deep sedimentary environments need for example to find available carbon sources enabling the least energy expenses for a maximized yield. Specific communities are known to be adapted to these low energy environments, but much remains to be understood regarding their development strategies. In a study developed in the framework of the ICDP Dead Sea Deep Drilling Project, we report biomarker evidence for the recycling of archaeal membrane lipids by Bacteria in extreme facies of the Dead Sea deep sediments. Isoprenoid wax esters derived from the recombination of hydrolyzed products of archaeal cell wall constituents were retrieved in gypsum and/or halite deep sedimentary deposits down to 250 m below the lake floor. They suggest the reutilization of dead archaeal biomass by halophilic heterotrophic bacteria. Such integration of exogenous material from one domain of life in another is a newly observed strategy for coping with extreme energy-limiting environments and allows bacterial communities of the Dead Sea subsurface to build carbon stocks and produce water in this extreme environment

Plant Wax n-Alkane and n-Alkanoic Acid Signatures Overprinted by Microbial Contributions and Old Carbon in Meromictic Lake Sediments

International audienceSpecific n-alkanes and n-alkanoic acids are commonly used as biomarkers in paleoenvironmental reconstruction, yet any individual homologue may originate from multiple biological sources. Here we improve source and age controls for these compounds in meromictic systems by measuring the radiocarbon (C-14) ages of specific homologues preserved in twentieth century Lake Pavin (France) sediments. In contrast to many studies, C-14 ages generally decreased with increasing carbon chain length, from 7.3 to 2.6 ka for the C-14-C-30 n-alkanoic acids and from 9.2 to 0.3 ka for the C-21-C-33 n-alkanes. Given a known hard water effect, these values suggest that aquatic microbial sources predominate and contributed to most of the homologues measured. Only the longest chain n-alkanes exclusively represent inputs of higher plant waxes, which were previously sequestered in soils over centennial to millennial timescales prior to transport and deposition. These findings suggest that biomarker source and age should be carefully established for lacustrine settings

New Insights Into Bacterial Wax Ester Biosynthesis, Natural Occurrence And Adaptive Role In Anaerobic Environments

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