Fatty acids derived from phospholipids and lipopolysaccharides were investigated from 33 taxonomically different organisms (bacteria, fungi and plant cells) known a priori to inhabit soil (except E. coli). The extended extraction procedure used, liberated non-ester-linked fatty acids in addition to ester-linked fatty acids, hydroxy substituted fatty acids in three different fractions. The amount of non-ester-linked fatty acids was as high as 70% of the total phospholipid fatty acids in some fungi and varied considerably in different organisms. The cis vaccenic acid constituted about 50% of phospholipid fatty acids in selected bacteria belonging to the alpha subclass of Proteobacteria. These fatty acids were not found in other selected organisms. A large amounts of branched chain fatty acids were found in various organisms. If the branching are localised on positions other than iso and anteiso they were strong indicators for gram positive bacteria. The cyclopropyl fatty acids are mainly localized in gram negative bacteria. The beta hydroxy fatty acid of the outer membrane are widespread among bacterial taxa and fungi. These fatty acids are not recommended to use as "signature" fatty acids for gram negative bacteria.