Signature Lipid Biomarker Analysis for Quantitative Assessment In Situ of Environmental Microbial Ecology

Examination of the lipid components of microbes in recent sediments has provided a convenient, quantitative, and comprehensive method to define the viable biomass, community composition, and nutritional/physiological activities of the biological communities in the sediments. The lipid extraction provides both a concentration and purification of the lipids from the soils and sediments. The subsequent fractionation, purification, and derivatization, sets up the definitive separation and structural identification by capillary gas chromatography with mass spectral identification of each component. As a part of this signature lipid biomarker (SLB) analysis, the lipid extraction also lyses the cells and allows for recovery of purified nucleic acids for subsequent gene probing with and without enzymatic amplification. This polyphasic analysis adds powerful specificity to the analysis of community microbial ecology. Since the SLB analysis involves detection by mass spectrometry, rates of incorporation of non-radioactive 13C and 15N mass-labeled precursors into signature biomarkers can be utilized to gain insight into specific metabolic activities. Application of electrospray and other external ionization sources to ion-trap mass spectrometry will greatly increase the specificity and sensitivity of the SLB analysis.