Microbial Fatty Acid Fingerprinting in Paddy Rhizosphere: GC-FAME Analytical Approach

Abstract Microbial identification aids in understanding microbial diversity and ecological roles. Characterization techniques rely mainly on the DNA or RNA composition of bacteria and biochemical parameters tested in laboratories. Bacterial fatty acid composition is a reliable biochemical fingerprint that supports accurate bacterial identification, classification, and understanding of evolutionary relationships. Bacteria contain straight and branched-chain fatty acids, unusual fatty acids, hydroxy acids, internally branched fatty acids, ω-cyclic fatty acids, hydroxy and cyclopropane fatty acids, dicarboxylic fatty acids, ladderane fatty acids. The fatty acid profile of an organism is a stable chemotaxonomic marker because it generates species specific profiles that can differentiate species and genera. It also reflects the genetic makeup of an organism since fatty acid biosynthesis pathways are genetically encoded thus aiding phylogenetic inference. Determination of fatty acid profile of an organism can also indicate its ecological adaptations. Techniques like gas chromatography–fatty acid methyl ester (GC-FAME) analysis allow for rapid and reproducible profiling for confirming bacterial identity from environmental and clinical samples. It can complement other molecular identification methods by providing phenotypic data to resolve ambiguities if any that may arise in genetic classification. Fatty acid composition can be compared with standard fatty acid databases using the Sherlock Microbial Identification System (MIS) a system that generates a Similarity Index and expresses the relative distance between the unknown entry profile and the closest library match. This review highlights GC-FAME analysis for microbial identification and discusses the characterization of the paddy rhizosphere bacterium, Brevibacillus centrosporus , through GC-FAME analysis, which demonstrated potential bioinoculant activity by enhancing seed germination and shoot growth in Vigna radiata.