PMID:9215808
| Citation |
Ivanova, AB, Glinsky, GV and Eisenstark, A (1997) Role of rpoS regulon in resistance to oxidative stress and near-UV radiation in delta oxyR suppressor mutants of Escherichia coli. Free Radic. Biol. Med. 23:627-36 |
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| Abstract |
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. |
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| Keywords |
Bacterial Proteins/genetics; Bacterial Proteins/physiology; DNA-Binding Proteins; Escherichia coli/genetics; Escherichia coli Proteins; Mutation; Oxidative Stress; Recombinant Fusion Proteins; Regulon; Repressor Proteins/genetics; Sigma Factor/genetics; Sigma Factor/physiology; Transcription Factors/genetics; Transcription, Genetic; Ultraviolet Rays; beta-Galactosidase/genetics |
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