DETERMINATION OF PHOSPHOLIPID-DERIVED AND LIPOPOLYSACCHARIDE-DERIVED FATTY-ACIDS AS AN ESTIMATE OF MICROBIAL BIOMASS AND COMMUNITY STRUCTURES IN SOILS

Several soils subject to different cultivation and management practice s were examined by analysis of fatty acid profiles derived from phosph olipids and lipopolysaccharides, using an improved sequential method w hich is capable of measuring ester-linked and non-ester-linked phospho lipid fatty acids (EL-PLFA, NEL-PLFA, respectively) and the hydroxy fa tty acids in lipopolysaccharides. A good correlation was obtained (r>0 .90) between the soil biomass and total EL-PLFA in the soils investiga ted, which ranged from forest soils to a variety of agricultural soils . Elucidation of the composition of the community structure was an add itional task. Eukaryotes can be differentiated from bacteria by the pr esence of polyunsaturated and omega-hydroxy fatty acids, both of which were much more abundant in the OF layer of the forest soil than in th e remaining samples. A relatively low proportion of monomethyl branche d-chain saturated fatty acids was obtained in the forest OF horizon, t hese being indicators for Gram-positive bacteria and actinomycetes. Va rious subclasses of proteobacteria produce beta and mid-chain hydroxy fatty acids, which occur primarily in agricultural soils. The ratios b etween monounsaturated fatty acids and saturated fatty acids seem to b e very useful parameters of soil environmental conditions. In addition , on the basis of the differences in composition of the NEL-PLFA and h ydroxy fatty acids of lipopolysaccharides, clear indications for the c ommunity structure of various soils were obtained. In the forest soils much more abundant anaerobic micro-organisms and relatively less abun dant proteobacteria were present than in the other soils. In the culti vated soils, however, the proportion of Gram-negative bacteria was con siderably higher. Furthermore, eukaryotes appeared to be pre-dominant in the soils once used for a manure deposit site.