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

完整的极性膜脂是海洋沉积物中普遍存在的痕量化合物，被认为是活微生物细胞的诊断标志。糖苷古菌二醚和四醚这一特定的IPL组分的优势表明，古生菌构成了微生物生物量的主要部分(Lipp等人，自然，454,991-994,2008)。无机磷浓度与总有机碳之间存在着显著的相关性。我们认为，这种关系反映了海洋沉积生物圈的一个基本性质，可以用来估计生物量。然而，我们目前的数据集仍然强烈偏向于海洋富营养化部分的沉积物。因此，我们建议将我们的环境调查扩展到一个真正具有全球代表性的数据集，其中包括不同的公海环境，并补充基于散装电池密度的现有和相应的数据集。我们希望限制控制海洋沉积物中微生物生物量分布的因素。其他实验调查将侧重于主要IPL类别的环境持久性，并研究沉积IPL化石部分的潜在存在。我们还建议研究选定的古生代的生长条件与IPL组成之间的关系，以了解海洋地下沉积物中糖苷醚类脂的优势。我们的研究将提高我们对沉积生物圈、其全球范围和广泛的分类组成的理解，推进复杂环境样品中微生物生物量的检测技术，并发展年轻研究员Julius Lipp的职业生涯。

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.