Phospholipid fatty acid - A bioindicator of environment monitoring and assessment in soil ecosystem

The key driving factor for sustainable agriculture is soil ecosystem, where pivotal services are provided by the soil biota, 'the biological engine of the earth', which can act as early warning signals of ecosystem health, and can be of use in environmental diagnosis. Phospholipid fatty acid (PLFA) profiles offer sensitive reproducible measurements for characterizing the numerically dominant portion of soil microbial communities without cultivating the organisms. The technique gives estimates of both microbial community composition and biomass size, and results represent in situ conditions in the soil. PLFA analysis has been used to detect various environmental stresses in the soil and was found to be more discriminatory than other methods. A set of certain specific PLFAs, viz. trans/cis ratio of monounsaturated fatty acids (16 : 1ω7, 18: 1ω7), cyclopropyl (cy17:0 and cy19:0) fatty acids, and fungal PLFA (18:2w6) were able to distinguish the stressed environmental conditions such as heavy metal addition, tillage, organic compound toxicity, starvation and increased soil temperature. This set of PLFA needs further testing and validation in the wide spectrum of environmental stressed conditions under diverse ecosystems, before its implication as bioindicators of environment monitoring and assessment at the global scale.