Signature lipid biomarkers for in situ microbial biomass, community structure and nutritional status of deep subsurface microbiota in relation to geochemical gradients. Final technical report

To obtain a better understanding of the microbial ecology of the deep subsurface, it was necessary to employ alternate techniques for the identification of microorganisms in situ. Classical microbiological techniques assay only those organisms which are culturable with bias occurring towards the media selected. Since culturable microorganisms typically represents only 0.1 to 10% of the extant microbiota, techniques for the direct assay of microorganisms in situ were needed. The analysis of cellular lipid biomarkers is a technique whereby microbial communities can be assayed directly in a variety of environmental matrices. Through the quantitative recovery of lipid biomarkers, estimations of cell biomass, community composition and community nutritional and/or physiological status can be obtained.