Nucleotide sequence of the spo0B gene of Bacillus subtilis and regulation of its expression

The spo0B gene is one of the genes involved in initiation of sporulation of Bacillus subtilis. This gene, previously cloned into the pHV33 shuttle vector, is expressed in Escherichia coli and B. subtilis. We have determined the sequence of 1118 base pairs (bp) of the DNA insert carrying the spo0B gene. The promoter sequence of this gene shows the canonical T-A-T-A-A-T region at 10 bp from the transcriptional start (-10 region) but an unusual sequence, T-T-T-T-C-T-, in the -35 region. The nucleotide sequence shows an open reading frame encoding a 192-amino-acid polypeptide of Mr 22,542, which is close to the molecular weight of the spo0B product synthesized in E. coli minicells. To investigate the regulation of the spo0B gene under a variety of physiological conditions, we constructed an in-frame fusion between the spo0B promoter proximal region and the lacZ gene of E. coli. This hybrid gene was subsequently integrated into the B. subtilis chromosome, and the beta-galactosidase activity was measured. It was found that the spo0B gene is preferentially expressed during exponential growth; it is not induced by exhaustion of the growth medium nor repressed by glucose.