Expression of stage II genes during sporulation in Bacillus subtilis.

Two RNA polymerase sigma factors, sigma F and sigma E, are produced during the first two hours of endospore formation in Bacillus subtilis. Transcription of the structural genes for these factors is activated about one hour after the start of endospore formation. The operon encoding sigma F is transcribed by RNA polymerase containing sigma H, another secondary sigma factor, whereas the operon encoding sigma E is transcribed by RNA polymerase containing sigma A, the primary sigma factor in growing cells. Evidently, the coordinate temporal control of these transcriptional units is mediated by a factor other than the sigma factors, possibly by the DNA-binding protein encoded by spo0A. Both sigma F and sigma E activities are also regulated by mechanisms operating after transcription.