Catabolite regulation of Bacillus subtilis acetate and acetoin utilization genes by CcpA

The Bacillus subtilis acsA (acetyl coenzyme A synthetase) and acuABC (acetoin utilization) genes were previously identified in the region downstream from the ccpA gene, which encodes a protein required for catabolite repression of the amyE (a-amylase) gene. The acsA and acuABC genes are divergently transcribed, with only 20 bp separating the-35 sequences of their promoters. Expression of these genes was maximal in stationary phase and was repressed by the addition of glucose to the growth medium. Two sites resembling amyO, the cis-acting regulatory target site for amyE, were identified in the acsA and acuABC promoter regions. Glucose repression of acsA and acuABC transcription was dependent on both CcpA and the amyO-like sequences. The presence of readily metabolizable carbon sources in the growth medium generally results in repression of genetic systems for utilization of secondary carbon sources and activa-tion of pathways involved in excretion of excess carbon. In Bacillus species, the mechanisms for response to carbon excess are not well understood, although it is evident that cyclic AMP is not the effector, as it is in Escherichia coli (for a review, se