THE KDGRKAT OPERON OF BACILLUS-SUBTILIS - DETECTION OF THE TRANSCRIPTAND REGULATION BY THE KDGR AND CCPA GENES

Transcription of a new catabolic operon in Bacillus subtilis, involved in the late stager of galacturonic acid utilization, has been studied . The operon consists of four genes: kdgR, encoding the putative regul ator protein; kdgK, encoding 2-keto-3-deoxygluconate kinase; kdgA, enc oding 2-keto-3-deoxygluconate-6-phosphate aldolase; and kdgT, encoding a transporter. These four genes are organized in one transcriptional unit and map at 198 degrees of the B. subtilis chromosome. Primer exte nsion experiments and Northern blot analysis show that an active sigma (A)-dependent promoter precedes kdgR and transcription is terminated a t the putative rho-independent terminator downstream of kdgT. The oper on is negatively regulated by the kdgR and ccpA gene products, which b elong to the Lad family of transcription regulators. The expression of the genes in this operon can be induced by galacturonate and strongly repressed when glucose is present in the growth medium. Knockout muta tions in genes kdgR and ccpA remove, respectively, the effects of gala cturonate and glucose on the transcription of this operon.