Augmentation of Cyclopropane Fatty Acid Synthesis under Stringent Control in Escherichia coli¹²

An abrupt increase of cyclopropane fatty acid (CFA) occurred concomitant with a decrease of the corresponding unsaturated fatty acids in CP78 (rel+) of Escherichia coli at the onset of the stationary growth phase, whereas such variations were slight in CP79 (rel-). When the cells were starved for isoleucine, the CFA content increased in CP78 but not in CP79. The rate of 14C-incorporation from [methyl-14C]methionine into CFAs increased in CP78 abut two-fold due to the starvation. The apparent level of CFA synthase also increased due to the starvation. These results that the CFA formation is augmented under stringent control.