Phospholipid fatty acid analysis and its applications in microbial ecology

The quantitative description of microbial community is one of the difficult tasks for microbial ecologist. Conventional cultivation techniques cannot be used to fully characterize most soil microorganisms in respect that most of species cannot be cultured. Using phospholipid fatty acids (PLFA) profiles to characterize microbial communities can overcome the limitation of traditional techniques, because it doesn't require the removal and the culture of the microbes. The membrane phospholipids exist in all living cellular membrane. They are not found in storage products or in dead cells by reason of rapidly degradation after cells dying. PLFA don't vary much in a cell which they form a part, and keep reasonably constant amounts as cells occur in nature. The analysis of the ester-linked fatty acids of the phospholipids makes use of capillary gas chromatography and mass spectrometry. With such technique, the component of each PLFA and the shift in PLFA pattern can be quantitatively analyzed. PLFA profiles, consisted of quantitative determination of each PLFA component and the shift in PLFA patterns, can provide comprehensive information for detecting the microbial community. Several fatty acids are known to be “signatures” of subsets of microbial community. Therefore, the specific PLFA profiles can be used to characterize different groups of bacteria. Furthermore, a phospholipid pattern change in the related samples could be indications of a shift in microbial community. In fact, the PLFA technique has been used to illuminate the shifts in microbial community for adapting to the changed environmental conditions under wide range of soil types, management practices, climatic origins, etc. Although PLFA profile is unable to identify microorganisms at a species and strain level, it produces descriptions of the whole microbial community. It can be utilized to measure the viable microbial biomass and the community structure in environmental samples, such as sediments, soils, etc. Because of relative simplicity and good resolution, PLFA has become more and more popular. We introduced an analysis measurement of PLFA profiles and reviewed the published applications, including the assessment of microbial biomass, community structure, nutritional status and metabolic activity, in microbial ecology.