Gumpert, J.Schade, W.Krebs, D.Baykousheva, S.Ivanova, E.Toshkov, A.The comparative fatty acid analysis of extractable and non-extractable lipids of Escherichia coli W 1655 F+ and its stable protoplast type L-form shows quantitative as well as qualitative differences. From 10 different fatty acids obtained, 16:0, 17:0 and 18:0 were present at about the same quantities in the lipid fractions of the bacterial and L-form. The absence of larger amounts of 12:0, 14:0, and 14:beta-hydroxy fatty acids in the non-extractable L-form lipids reflects the loss of the cell wall in L-form cells. The 16:1 fatty acid was found in L-form lipids, only. This qualitative difference and the 2-3 times higher content of 18:1 in L-form lipids and the 7 times lower content of cyc-19:0 in extractable lipids of the L-form may be interpreted as alterations characteristic of the changed composition of the cytoplasmic membrane in the L-form cells.enBaykouchevaEscherichia coliL-formslipidsfatty acidsArticle