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.