Glucose stimulates a decrease of the fatty acid saturation degree in Acinetobacter calcoaceticus

The fatty acid composition of Acinetobacter calcoaceticus 69-V was determin ed under various growth conditions. Saturated, unsaturated, and; hydroxy fa tty acids with chain lengths of 12-18 carbon atoms predominated in the fatt y acid profile. With acetate or propanol as growth substrates, the ratio of saturated to unsaturated fatty acids varied with changes in the temperatur e. This was the only adaptive mechanism detected that compensated for the p hysical effects of temperature alterations on the cell membranes. The fatty acid composition of A. calcoaceticus grown at 40 degrees C had: a saturati on degree of approximately 50%; after growth at 20 degrees C it was approxi mately 35%. In the presence of a carbon and energy source, A. calcoaceticus was able to respond Co temperature reductions under oxic conditions regard less of whether fatty acid biosynthesis was inhibited or not. This suggests an aerobic mechanism of fatty acid biosynthesis and the involvement of a f atty acid desaturase system. Addition of the non-growth substrate, glucose, helped the organism to adapt to lower temperature. The molecular mechanism of the aid is not: really understood. The oxidation of glucose could provi de die desaturase either with electrons directly via a pyrrolo-quinoline-qu inone-linked glucose dehydrogenase or with NADH after fatty acid degradatio n has been initiated by ATP generated by the oxidation of glucose.