A PHO REGULON PROMOTER INDUCED UNDER SPORULATION CONDITIONS

Sporulation-induced alkaline phosphatases (APases) of Bacillus subtili s require the products of the sporulation stage-0 genes and certain st age-II genes, including the spoIIA operon, for induction. Mutations in either sapA or sapB bypass this requirement [Piggot and Taylor, J. Ge n. Microbiol. 10 (1977) 69-80], resulting in APase production in a spo IIA sapA or spoIIA sapB strain, under sporulation conditions. B. subti lis has multiple structural genes encoding APases, which are induced e ither by phosphate starvation or during sporulation, or under both con ditions. We report studies designed to determine which APase(s) were b eing expressed in the sap mutants, and from which promoters. phoB (for merly phoAIII), one of the structural genes encoding an APase in B. su btilis, is expressed under both sporulation and phosphate starvation c onditions, but from separate promoters [Chesnut et al., Mol. Microbiol . 5 (1991) 2181-2190]. The spoIIA sapA and spoIIA sapB strains express phoB under sporulation conditions. Interestingly, the expression of p hoB during sporulation was from P-v, the phosphate starvation-inducibl e promoter of phoB, rather than from P-s, the sporulation-specific pro moter. Since the induction of phosphate starvation-inducible promoters during phosphate limitation requires the phoPR operon [Miki et al., G enetics 52 (1965) 1093-1100], we asked if the phoPR products were invo lved in regulating P-v expression under sporulation conditions. The ph oPR genes are transcribed under sporulation conditions, regulated by s apA and sapB under sporulation conditions, and required for expression from P-v under sporulation conditions.