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. 1997;23(4):627-36. doi: 10.1016/s0891-5849(97)00013-0.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 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


  • Bacterial Proteins
  • DNA-Binding Proteins
  • Escherichia coli Proteins
  • Recombinant Fusion Proteins
  • Repressor Proteins
  • Sigma Factor
  • Transcription Factors
  • oxyR protein, E coli
  • sigma factor KatF protein, Bacteria
  • beta-Galactosidase