The effect of novobiocin, an inhibitor of DNA gyrase, on the expression ofgenes for fatty acid desaturases in the cyanobacterium Synechocystis sp PCC 6803

We studied the effects of the inhibitor of DNA gyrase, novobiocin, on the e xpression of desaturase genes and fatty acid (FA) desaturation in the cyano bacterium Synechocystis sp. PCC 6803. Upon a decrease in the temperature of the growth medium, three genes encoding Delta 12, Delta 6, and omega 3 FA desaturases were induced in Synechocystis cells. Novobiocin (50 mu g/ml) su ppressed the accumulation of the corresponding mRNAs to various extent. The desB gene encoding omega 3 desaturase was most susceptible. Novobiocin com pletely inhibited the low-temperature-induced transcription of this gene, t he accumulation of the corresponding protein, and the formation of the omeg a 3 unsaturated FA. In the presence of novobiocin, the novobiocin-resistant mutant cells of Synechocystis responded to the low-temperature treatment i n the same way as the wild-type cells in the absence of an antibiotic. Thus , the inhibitor of DNA gyrase, novobiocin, could specifically inhibit the l ow-temperature induction of desaturase genes and the accumulation of polyun saturated FA.