Regulation of the fatty acid composition of the membrane phospholipids of Escherichia coli.

An increase in the dosage of the fabA gene, which codes for the enzyme beta-hydroxydecanoyl thioesterase, causes an increase in the unsaturated fatty acyl content of the phospholipids. This increase is small in cells growing at a constant temperature. However, if cells grown at 37 or 42 degrees are shifted to 15 degrees , the rate of unsaturated fatty acyl moiety synthesis approaches twice the rate of a normal strain. These results indicate that the ratio of unsaturated to saturated fatty acyl groups in phospholipids is partially determined by the levels of at least this fatty acid biosynthetic enzyme.