Poster: Lipids & Related Molecules

Abs # 857: Membrane lipid analysis of the soil microecology in S. rolfsii infested tomato fields

Presenter:	Sams, Carl E.
Authors	Lyons, Martin T. (A)   Sams, Carl E. (A)   Peacock, Aaron D. (B)   White, David C. (B)
Affiliations:	(A): Department of Plant Sciences, The University of Tennessee (B): Center for Biomarker Analysis, The University of Tennessee

Phospholipid fatty acids (PLFA) are major components of the cellular membranes of all living organisms. PLFA are discriminatory enough to allow various subsets of the microbial community to be identified. In addition to giving evidence of the phenotypic properties of the community, PLFA analysis gives in situ indications of growth rate, aerobic/anaerobic balance, exposure to toxicity, and unbalanced growth. Also many subsets of the soil microbial community respond to conditions in their environment with shifts in lipid composition. When extracted from the rhizosphere or bulk soil PLFAs provide a quantitative measure of viable biomass. Commercial tomato production can be severely effected by the highly virulent fungal pathogen Sclerotium rolfsii. The ability of this pathogen to proliferate and invade the roots of a host is influenced by the soil microbial community structure. PFLA analysis has been able to link characteristic soil microbial community compositions with disease suppression in tomatoes. Plants grown in soils amended with biologically based treatments, such as biofumigation and composts, displayed decreased fungal infection and increased yields compared to controls. These treatments produced an enhanced microbial biomass and a shift in community composition. PLFA quantification revealed a relative increase in monounsaturated signature lipid biomarkers, indicating an elevated population of gram-negative bacteria, and a decrease in polyunsaturates proportional to total biomass. The latter indicates a decrease in microeukaryotes in relation to overall biomass counts. Specific lipid biomarkers such as the fungal indicator 18:2w6 were detected at lower ratios in the compost amended plots when compared with bacterial biomarkers.