Regulation of theBacillus subtilis furandperRGenes by PerR: Not All Members of the PerR Regulon Are Peroxide Inducible

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Abstract
PerR is a ferric uptake repressor (Fur) homolog that functions as the central regulator of the inducible peroxide stress response inBacillus subtilis. PerR has been previously demonstrated to regulate themrgA,katA,ahpCF,hemAXCDBL, andzosAgenes. We now demonstrate that PerR also mediates both the repression of its own gene and that offur. Whereas PerR-mediated repression of most target genes can be elicited by either manganese or iron, repression ofperRandfuris selective for manganese. Genetic studies indicate that repression of PerR regulon genes by either manganese or iron requires PerR and is generally independent of Fur. Indeed, in afurmutant, iron-mediated repression is enhanced. Unexpectedly, repression of thefurgene by manganese appears to require both PerR and Fur, but only PerR binds to thefurregulatory region in vitro. Thefurmutation appears to act indirectly by affecting cellular metal ion pools and thereby affecting PerR-mediated repression. While many components of theperRregulon are strongly induced by hydrogen peroxide, little, if any, induction offurandperRcould be demonstrated. Thus, not all components of the PerR regulon are components of the peroxide stimulon. We suggest that PerR exists in distinct metallated forms that differ in DNA target selectivity and in sensitivity to oxidation. This model is supported by the observation that the metal ion composition of the growth medium can greatly influence the transcriptional response of the various PerR regulon genes to hydrogen peroxide.