FapR, a bacterial transcription factor involved in global regulation of membrane lipid biosynthesis.

Bacterial cells exert exquisite control over the biosynthesis of their membrane lipids, but the mechanisms are obscure. We describe the identification and purification from Bacillus subtilis of a transcription factor, FapR, that controls the expression of many genes involved in fatty acid and phospholipid metabolism (the fap regulon). Expression of this fap regulon is influenced by antibiotics that specifically inhibit the fatty acid biosynthetic pathway. We show that FapR negatively regulates fap expression and that the effects of antibiotics on fap expression are mediated by FapR. We further show that decreasing the cellular levels of malonyl-CoA, an essential molecule for fatty acid elongation, inhibits expression of the fap regulon and that this effect is FapR dependent. Our results indicate that control of FapR by the cellular pools of malonyl-CoA provides a mechanism for sensing the status of fatty acid biosynthesis and to adjust the expression of the fap regulon accordingly.