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The presence of excess glucose in growth media prevents normal sporulation of Bacillus subtilis. The crsA47 mutation, located in the gene for the vegetative phase sigma factor ( A ) results in a glucose-resistant sporulation phenotype. As part of a study of the mechanisms whereby the mutation in A overcomes glucose repression of sporulation, we examined the expression of genes involved in sporulation initiation in the crsA47 background. The crsA47 mutation had a significant impact on a variety of genes. Changes to stage II gene expression could be linked to alterations in the expression of the sinI and sinR genes. In addition, there was a dramatic increase in the expression of genes dependent on the minor sigma factor H . This latter change was paralleled by the pattern of spo0H gene transcription in cells with the crsA47 mutation. In vitro analysis of RNA polymerase containing A47 indicated that it did not have unusually high affinity for the spo0H gene promoter. The in vivo pattern of spo0H expression is not predicted by the known regulatory constraints on spo0H and suggests novel regulation mechanisms that are revealed in the crsA47 background.

We have found that sporulation in Bacillus subtilis crsA47 mutants does not require the H -dependent promoter of the spo0A gene. This implies that the glucose-resistant sporulation phenotype of this strain is not related to the switch from the vegetative-stage A -dependent promoter to the H -dependent promoter at the spo0A gene.The Bacillus subtilis response regulator Spo0A is at the center of a complex signal transduction network that controls entry into the developmental pathway for endospore formation. The spo0A gene has two promoters that are differentially regulated, spo0Apv and spo0Aps. The spo0Apv promoter is weakly expressed during vegetative growth and is transcribed by RNA polymerase containing the major vegetative-phase sigma factor, A (4). spo0Aps is induced during the initial stages of sporulation and requires both RNA polymerase containing the alternate sigma factor, H , and phosphorylated Spo0A (Spo0AϳP) for expression (20,23). As the spo0Aps promoter is activated, transcription from the spo0Apv promoter normally declines due to repression by Spo0AϳP; thus, there is a promoter switch. The activation of the spo0Aps promoter during sporulation has been reported to be required for the accumulation of sufficient Spo0AϳP to fully activate the transcription of stage II sporulation genes (5,13,22,23).In wild-type B. subtilis, the spo0A promoter switch has been shown to be repressed by excess glucose (26), which blocks sporulation at an early stage (3,11,21,25). One of the mutations that lead to glucose-resistant sporulation, crsA47 (4, 24), alters the gene for the major vegetative-stage sigma factor, A

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