Role of rpoS regulon in resistance to oxidative stress and near-UV radiation in delta oxyR suppressor mutants of Escherichia coli.
Escherichia coli delta oxyR mutants are hyper-sensitive to oxidative agents but this sensitivity is reversed to hyper-resistance in delta oxyR suppressor strains (delta oxyRsup; Greenberg, J.T. and Demple, B. 1988. EMBO J. 7:2611-2618). Also, delta oxyR mutants have increased mutation rates that are also reversed in delta oxyRsup. We now report that the rpoS regulon may have a role in determining hyper-resistance and loss of hyper-mutability of delta oxyRsup. Delta oxyRsup cells were also resistant to near-ultraviolet radiation (near-UV) and survived longer in stationary phase than delta oxyR cells. In delta oxyRsup cells elevated beta-galactosidase expression from a rpoS::lacZ promoter fusion and significant overproduction of RpoS protein was observed. These increases were accompanied by substantial elevation in transcription of rpoS-dependent genes as determined by beta-galactosidase expression from katE::lacZ, dps::lacZ, and xthA::lacZ promoters. Catalase HPI and HPII activities were also increased. When rpoS::Tn10 was transduced into delta oxyRsup, phenotypes switched back to hyper-sensitive, hyper-mutable and reduced catalases I and II. Individual delta oxyR colonies exhibited significant clonal variability in beta-galactosidase expression from rpoS::lacZ promoter. These results provide further evidence of the functional and regulatory overlap between two major anti-oxidant defense systems of bacteria.
Ivanova
A B
AB
Cancer Research Center, University of Missouri, Columbia 65201, USA.
Glinsky
G V
GV
Eisenstark
A
A
D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology; D004268:DNA-Binding Proteins; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D009154:Mutation; D018384:Oxidative Stress; D011993:Recombinant Fusion Proteins; D018085:Regulon; D012097:Repressor Proteins / Q000235:genetics*; D012808:Sigma Factor / Q000235:genetics* / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic; D014466:Ultraviolet Rays; D001616:beta-Galactosidase / Q000235:genetics
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D012808:Sigma Factor; D014157:Transcription Factors; C499299:oxyR protein, E coli; C069567:sigma factor KatF protein, Bacteria; D001616:beta-Galactosidase