DIFFERENTIAL REGULATION OF SPO0A TRANSCRIPTION IN BACILLUS-SUBTILIS - GLUCOSE REPRESSES PROMOTER SWITCHING AT THE INITIATION OF SPORULATION

We have shown by S1 nuclease mapping with in vivo transcripts that the differential expression of a sporulation-regulatory gene, spo0A, is regulated by switching of two discrete promoters during the initiation of sporulation in Bacillus subtilis; vegetative mRNA was transcribed from an upstream promoter (P(v), vegetative promoter), and sporulation-specific mRNA was transcribed from the other promoter (P(s), sporulation-specific promoter) about 150 bp downstream of the P(v) promoter. Transcription from the P(v) promoter was at a low level and shut off at T0.5. On the other hand, transcription from the P(s) promoter was strongly induced at T0.5 and increased until T2.5. In the presence of 2% glucose, P(v)-directed transcription was not shut off and was observed even at T1.5, whereas the induction of P(s)-directed transcription was completely repressed. A mutant in which the spo0A gene was transcribed only from the P(s) promoter could sporulate normally in the presence of 0.1% glucose but could not sporulate at all in the presence of 2% glucose. In a catabolite-resistant sporulation mutant carrying crsA47 (sigA47), a mutation within the gene encoding sigma-(A), normal promoter switching from P(v) to P(s) was observed in the presence of 2% glucose.