, Volume 31, Issue 2, pp 129-137

Trans unsaturated fatty acids in bacteria

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The occurrence oftrans unsaturated fatty acids as by-products of fatty acid transformations carried out by the obligate anaerobic ruminal microflora has been well known for a long time. In recent years, fatty acids withtrans configurations also have been detected in the membrane lipids of various aerobic bacteria. Besides several psychrophilic organisms, bacteria-degrading pollutants, such asPseudomonas putida, are able to synthesize these compoundsde novo. In contrast to thetrans fatty acids formed by rumen bacteria, the membrane constituents of aerobic bacteria are synthesized by a direct isomerization of the complementarycis configuration of the double bond without a shift of the position. This system of isomerization is located in the cytoplasmic membrane. The conversion ofcis unsaturated fatty acids totrans changes the membrane fluidity in response to environmental stimuli, particularly where growth is inhibited due to the presence of high concentrations of toxic substances. Under these conditions, lipid synthesis also stops so that the cells are not able to modify their membrane fluidity by any other mechanism.