Identification of ς B -Dependent Genes in Bacillus subtilis Using a Promoter Consensus-Directed Search and Oligonucleotide Hybridization

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Abstract
A consensus-directed search for ς B promoters was used to locate potential candidates for new ς B -dependent genes in Bacillus subtilis . Screening of those candidates by oligonucleotide hybridizations with total RNA from exponentially growing or ethanol-stressed cells of the wild type as well as a sigB mutant revealed 22 genes that required ς B for induction by ethanol. Although almost 50% of the proteins encoded by the newly discovered ς B -dependent stress genes seem to be membrane localized, biochemical functions have so far not been defined for any of the gene products. Allocation of the genes to the ς B -dependent stress regulon may indicate a potential function in the establishment of a multiple stress resistance. AldY and YhdF show similarities to NAD(P)-dependent dehydrogenases and YdbP to thioredoxins, supporting our suggestion that ς B -dependent proteins may be involved in the maintenance of the intracellular redox balance after stress.