Comparison of fatty acid methyl ester methods for characterization of microbial communities in forest and arable soil: Phospholipid fraction (PLFA) versus total ester linked fatty acids (EL-FAME)

Abstract

Phospholipid fatty acid (PLFA) and ester-linked fatty acid methyl ester (EL-FAME) extraction methods have been commonly used for estimating microbial biomass and characterizing microbial community composition in soil. However, to our knowledge, there is currently no comparison of these two methods across different ecosystems. A regression analysis for 8 different soils showed that there were significant linear relationships between PLFA and EL-FAME extracts (r2=0.97, 0.98 and 0.72, respectively) for determining the fungal (18:2ω6,9) and bacterial abundance and fungal-to-bacterial ratio (F:B ratio). However, regression lines of forest soils for fungal abundance and F:B ratio had a slight but significantly higher intercept than those of arable soils, i.e. higher EL-FAME:PLFA ratio for fungi in forests than those in arable soils. This might be due to that EL-FAME extracts may have additional factors such as physiological status of fungi and the inclusion of substantial amount of humic substances that affect quantitative determination of fungal biomass. Overall, EL-FAME method is simple and would produce similar results to PLFA method for bacteria in both quantitative and qualitative assessments when comparing different soils across ecosystems. However, for fungi, PLFA method would be more suitable than EL-FAME method.