The katX Gene, Which Codes for the Catalase in Spores of Bacillus subtilis, Is a Forespore-Specific Gene Controlled by s, and KatX Is Essential for Hydrogen Peroxide Resistance of the Germinating Spore

Previous work has shown that the katX gene encodes the major catalase in dormant spores of Bacillus subtilis but that this enzyme has no role in dormant spore resistance to hydrogen peroxide. Expression of a katX-lacZ fusion began at approximately h 2 of sporulation, and >75% of the katX-driven b-galactosidase was packaged into the mature spore. A mutation in the gene coding for the sporulation-specific RNA polymerase sigma factor s abolished katX-lacZ expression, while mutations in genes encoding s, s, and s did not. Induction of s synthesis in vegetative cells also resulted in katX-lacZ expression, while induction of s expression did not; the katX-lacZ fusion was also not induced by hydrogen peroxide. Upstream of the in vivo katX transcription start site there are sequences with good homology to those upstream of known s-dependent start sites. These data indicate that katX is an additional member of the forespore-specific s regulon. A mutant in the katA gene, encoding the major catalase in growing cells, was sensitive to hydrogen peroxide during sporulation, while a katX mutant was not. However, outgrowth of katX spores, but not katA spores, was sensitive to hydrogen peroxide. Consequently, a major function for KatX is to protect germinating spores from hydrogen peroxide.