Phospholipid-derived fatty acids
PLFA analysis may be combined with other techniques, such as stable isotope probing to determine which microbes are metabolically active in a sample.
PLFA analysis is a technique widely used for estimation of the total biomass and to observe broad changes in the community composition of the living microbiota of soil and aqueous environments.
There has been a surge of interest in PLFAs in recent years, evident from the large increase in peer-reviewed journal references on the subject.
Knowledge of the composition and metabolic activity of the microbiota in soils, water and waste materials is useful in optimizing crop production, in bioremediation and in understanding microbial ecosystems.
The GC-MS system is more expensive to purchase and maintain, requires considerable skill to operate, and is typically used for qualitative analysis only.
A commercially available, fatty-acid based microbial identification system (using GC-FID), which reproducibly names and quantitates the FAMEs, has been widely adopted for PLFA analysis.
Actinomycetes are active in decomposition of organic matter and give rise to the rich "earthy" smell of freshly tilled soils.
The PLFA profiles of these Gram-positive species have high percentages of biomarker branched-chain fatty acids such as 15:0 iso and 15:0 anteiso.
Thus, the sum of the iso and anteiso fatty acids in a PLFA analysis may provide an estimate of the abundance of the Gram-positive bacteria (other than actinomycetes) in the sample.
Thus, in PLFA analysis, the sum of monounsaturated and cyclopropane fatty acids may provide an estimate of the abundance of Gram-negative bacteria.
[3] Anaerobic bacteria in agriculture are primarily a factor in soils of low-oxygen levels such as occur in greater depths or of wet conditions such as in rice paddies.
Arbuscular mycorrhizae fungi (AMF) penetrate the walls of cortical cells of about 80% of all vascular plant families, generating a symbiotic relationship.
[16] Conventional, low-input and organic farming systems showed a rapid response of the soil microbial communities to wet/dry cycles and that increases in bacterial cyclopropyl fatty acids were useful to detect periods of stress.
[17] Lines of transgenic corn (maize) expressing Bacillus thuringiensis endotoxins were found to have small effect on soil microbial communities when compared by PLFA analysis to their non-transgenic isolines.
[19] Bioremediation has been studied using PLFA analysis of soil microbiota from sites contaminated by diesel fuel,[20] crude oil,[21] explosives,[22] olive mill waste,[23] pentachlorophenol,[24] coal tar[25] and PCBs.
[30] The diverse taxonomic groups in algae vary in abundance dependent on environmental conditions such as temperature, salinity, sunlight, and nutrient availability.
[34] By PLFA analysis, considerable spatial and seasonal variations were determined in a freshwater reservoir sedimentary microbial community.
[32] Coniferous forests are dependent on available nutrients in soil rather than agricultural fertilizers and thus are routinely colonized by symbiotic mycorrhizal fungi.
[37] The introduction of photosynthates through tree roots is a major source of carbon for soil microbiota and influences the composition of fungal and bacterial communities.
Complex microbial communities in activated sludge processes are needed for the stable removal efficiency of organic pollutants.
