ROLE OF CODY IN REGULATION OF THE BACILLUS-SUBTILIS HUT OPERON

Bacillus sabtilis mutants deficient in amino acid repression of the hi stidine utilization (hut) operon were isolated by transposon mutagenes is. Genetic characterization of these mutants indicated that they most likely contained transposon insertions within the codVWXY operon. The codY gene is required for nutritional regulation of the dipeptide per mease (dpp) operon. An examination of hut expression in a Delta codY m utant demonstrated that amino acid repression exerted at the hutO(A) o perator, which lies immediately downstream of the hut promoter, was de fective in a Delta codY mutant. The codY gene product was not required for amino acid regulation of either hut induction or the expression o f proline oxidase, the first enzyme in proline degradation. This indic ates that more than one mechanism of amino acid repression is present in B. subtilis. An examination of dpp and hut expression in cells duri ng exponential growth in various media revealed that the level of CodY -dependent regulation appeared to be related to the growth rate of the culture.