Microbial polar membrane lipids in marine sediments and their significance for subsurface life

点击翻译按钮获取中文摘要

Intact polar membrane lipids (IPLs) are ubiquitous trace compounds in marine sediments and are considered diagnostic markers for live microbial cells. The dominance of a particular group of IPLs, glycosidic archaeal di- and tetraethers, suggests that Archaea constitute a major fraction of microbial biomass (Lipp et al., Nature 454, 991-994, 2008). A significant relationship was observed between concentrations of IPLs and total organic carbon. We suggested that this relationship captures a fundamental property of the marine sedimentary biosphere and can be used to estimate quantities of biomass. However, our current data set is still strongly biased towards sediments in eutrophic parts of the ocean. Therefore we propose to extend our environmental survey to a truly globally representative data set that includes diverse open-ocean environments and complements existing and corresponding data sets based on concentrations of bulk cells. We want to constrain the factors that control the distribution of microbial biomass in marine sediments. Additional experimental investigations will focus on the environmental persistence of the major IPL classes and study the potential existence of a fossil fraction of sedimentary IPLs. We also propose to examine the relationship between growth conditions and IPL composition in selected Archaea in order to understand the dominance of glycosidic ether lipids in marine subsurface sediments. Our research will improve our understanding of the sedimentary biosphere, its global extent and broad taxonomic composition, advance technologies for the detection of microbial biomass in complex environmental samples, and develop the career of young investigator Julius Lipp.