Regulation of hexuronate utilization in Bacillus subtilis

We have identified a locus essential for galacturonate utilization in Bacil lus subtilis. Genes homologous to Escherichia coli and Erwinia chrysanthemi glucuronate and galacturonate metabolic genes were found in a cluster cons isting of 10 open reading frames (ORFs) in the B. subtilis chromosome, A mu tant of B. subtilis containing a replacement of the second and third ORFs w as unable to grow with galacturonate as its primary carbon source. Galactur onate induced expression from a sigma(A)-dependent promoter, exuP1, located upstream from the first ORF. The eighth ORF in this cluster (the exu locus ) encodes a LacI and GalR homolog that negatively regulated expression from exuP1, A 26-bp inverted repeat sequence centered 15 bp downstream from the exuP1 start point of transcription acted in cia to negatively regulate exp ression from exuP1 under noninducing conditions. Expression from the exuP1 promoter was repressed by high levels of glucose, which is probably mediate d by CcpA (catabolite control protein A). A sigma(E)-dependent promoter, ex uP2, was localized between the second and third ORFs and was active during sporulation.