Active biomass in the marine subsurface tracked by intact polar membrane lipids

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One primary goal of ODP/IODP is to obtain a detailed understanding of the nature of and the factors that control prokaryotic life in deeply buried sediments. We propose to extract information on the microbial ecology and the metabolism of prokaryotes from the structural and isotopic information encoded in intact polar lipids in deeply buried sediments. Intact polar lipids (IPLs) are ubiquitous membrane compounds that rapidly decay after death and thus select against fossil lipid signals that originated from an earlier point in the sediment's history. Studying sediments from ODP Legs 201, 204, and 207, we will address the two overarching research questions: (1) What ist the relationship between the sediments' geochemical regime and the structural diversity and abundance of IPLs? (2) What information regarding the metabolic pathways utilized by deeply buried prokaryotes in-situ can be inferred from down-core profiles of the carbon-isotopic compositions of bulk IPL fraction? The molecular-isotopic data will be integrated with complementary molecular-genetic data from national and international collaborators. The project seeks to support a PhD student... who will be integrated an international team of collaborators in Germany and the U.S.