ROLE OF RPOS (KATF) IN OXYR-INDEPENDENT REGULATION OF HYDROPEROXIDASE-I IN ESCHERICHIA-COLI

We present evidence showing that rpoS (katF) is a regulator of katG gene transcription in an oxyR-independent manner. Mutation of the rpoS gene in several different Escherichia coli strains caused a significant reduction in catalase HPI activity. In rpoS Delta oxyR double mutants, the level of HPI was considerably lower compared to the Delta oxyR parent strain, and was restored when transformed with an rpoS(+) plasmid. Overproduction of HPI in oxyR(-) suppressor strains was greatly diminished after inactivation of the rpoS gene and was accompanied by a substantial increase in sensitivity to menadione. Beta-galactosidase expression from a katG::lacZ promoter was lower in rpoS strains compared to rpoS(+) isogenic parents. Several Delta oxyR strains had detectable levels of katG transcription that was significantly diminished after rpoS gene inactivation.