One of Two OsmC Homologs in Bacillus subtilis Is Part of the ς B -Dependent General Stress Regulon

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Abstract
In this report we present the identification and analysis of two Bacillus subtilis genes, yklA and ykzA , which are homologous to the partially RpoS-controlled osmC gene from Escherichia coli . The yklA gene is expressed at higher levels in minimal medium than in rich medium and is driven by a putative vegetative promoter. Expression of ykzA is not medium dependent but increases dramatically when cells are exposed to stress and starvation. This stress-induced increase in ykzA expression is absolutely dependent on the alternative sigma factor ς B , which controls a large stationary-phase and stress regulon. ykzA is therefore another example of a gene common to the RpoS and ς B stress regulons of E. coli and B. subtilis , respectively. The composite complex expression pattern of the two B. subtilis genes is very similar to the expression profile of osmC in E. coli.