cis/trans isomerization of unsaturated fatty acids as possible control mechanism of membrane fluidity inPseudomonas putida P8

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Abstract
Exponentially growing cells ofPseudomonas putida had an increased ratio of saturated to unsaturated fatty acids in response to increased growth temperatures. Resting cells in which fatty acid biosynthesis was stopped reacted to a thermal increase by convertingcis-monounsaturated fatty acids totrans isomers.cis/trans isomerization of up to 60% of the unsaturated fatty acids was also activated by alcohols of different chain length. Their effective concentrations apparently depended on the lipophilic character of the alcohols. Also, a salt shock caused by the addition of NaCl resulted in the production oftrans fatty acids. However, cells that were adapted to growth media of high osmolarity synthesized cyclopropane fatty acids instead oftrans fatty acids. Activity ofcis/trans-isomerase was dependent on the growth phase and was significantly higher during logarithmic growth than during the stationary phase. The results of this study agree with the hypothesis that the isomerization ofcis intotrans unsaturated fatty acids is an emergency action of cells ofP. putida to adapt membrane fluidity to drastic changes of environmental conditions.

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