The TetR-type transcriptional regulator FasR of Corynebacterium glutamicum controls genes of lipid synthesis during growth on acetate.

The addition of fatty acids to either Escherichia coli or Bacillus subtilis elicits an elaborate cellular response of the lipid metabolism. We found that in Corynebacterium glutamicum the expression of accD1 encoding the β-subunit of the essential acetyl-CoA carboxylase is repressed in acetate-grown cells without the addition of fatty acids. The TetR-type transcriptional regulator NCgl2404, termed FasR, was identified and deleted. During growth on acetate, but not on glucose, 17 genes are differentially expressed in the deletion mutant, among them accD1, and fasA and fasB both encoding fatty acid synthases, which were upregulated. Determination of the 5' ends of accD1, fasA, fasB and accBC together with the use of isolated FasR protein identified the FasR binding site, fasO, which is located within the accD1 and fasA transcript initiation site thus blocking transcription by RNA polymerase binding directly. The identified fasO motif is present in C. efficiens or C. diphtheriae, too, and it is actually similarly positioned in these bacteria within the 5' ends of the accD1 and fasA transcripts, and a fasR orthologue is also present. The identification of the FasR-fasO system in Corynebacteriaceae might indicate a conserved transcriptional control of the unique lipid synthesis in these mycolic acid-containing bacteria.