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Gene Review

rpoS  -  RNA polymerase sigma factor RpoS

Salmonella enterica subsp. enterica serovar Typhimurium str. LT2

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Disease relevance of rpoS

  • Avirulence of LT2 strains of Salmonella typhimurium results from a defective rpoS gene [1].
  • Consistent with this, Salmonella typhi Ty2, a 'wild-type' strain used widely for the development of human live-vaccine candidates against typhoid fever, was shown to be defective for rpoS [2].

High impact information on rpoS

  • The katF (rpoS) gene mediates the expression of the Salmonella spv plasmid virulence genes during bacterial starvation [3].
  • Both unadapted and adapted rpoS and stiA mutants were hypersensitive to a H2O2 challenge [4].
  • Of the four core SSR loci, only rpoS and stiC mutants exhibited a defective C-starvation-inducible cross-resistance to H2O2 challenge [4].
  • Despite an increased sensitivity to acid stress and DNA damage, strains containing either an rpoS-null mutation or the rpoS(LT2) allele survived in J774 cells and bone marrow-derived macrophages as well as did otherwise isogenic strains with a wild-type rpoS allele [5].
  • We examined the effect of the rpoS allele on invasion and found that the rpoS status of the cell had no effect on the ability of the strains to invade intestinal epithelial cells in tissue culture [5].

Chemical compound and disease context of rpoS

  • sigma S (RpoS)-regulated lacZ transcriptional fusions in Salmonella typhimurium were identified from a MudJ transposon library by placing the rpoS gene under the control of the araBAD promoter and detecting lacZ expression in the presence or absence of arabinose supplementation [6].
  • Salmonella rpoS mutants were usually more sensitive to bactericidal levels of NaCl, sucrose, and glycerol [7].
  • The rpoS-dependent starvation-stress response locus stiA encodes a nitrate reductase (narZYWV) required for carbon-starvation-inducible thermotolerance and acid tolerance in Salmonella typhimurium [8].

Biological context of rpoS

  • However, these strains appear to survive stationary-phase and oxidative stresses as well as strains containing a wild-type rpoS allele [5].
  • Mutations in rpoS suppressed the mviA::Km-associated defects in growth rate, colony size, ASP production, and stress tolerance, suggesting that the effects of MviA on cell physiology occur via its control of sigmaS levels [9].
  • We have discovered that one component of a potential signal transduction system responsible for inducing rpoS expression is the product of the mouse virulence gene mviA+ [9].
  • Western blot (immunoblot) analysis of bacteria carrying PBAD::rpoS demonstrated arabinose-dependent rpoS expression during all phases of growth. sigma S-dependent gene expression of individual gene fusions was confirmed by P22-mediated transduction of the MudJ insertions into wild-type or rpoS backgrounds [6].
  • The rpoS gene was sequenced from these strains and three were found to harbour mutations including one deletion, one base-pair substitution resulting in a nonsense codon, and one insertion causing a frameshift resulting in an early stop codon [10].

Anatomical context of rpoS


Associations of rpoS with chemical compounds


Regulatory relationships of rpoS

  • In BALB/c mice, the rpoS aroA strain induced a systemic anti-LPS humoral response similar to that induced by the rpoS and aroA strains [14].
  • Mutants with an additional deletion in ompC revealed a reduced capacity of intestinal colonisation-inhibition when compared to the control strains and both the single rpoS and the phoP deletion mutants [15].

Other interactions of rpoS

  • A fis mutant of S. enterica serovar Typhimurium showed a ninefold increase in expression from the major rpoS promoter (PrpoS) during exponential growth, whereas expression during SP was unaffected [16].
  • The rpoS (katF) gene, which encodes a RNA polymerase sigma factor (sigma s), regulates the virulence of Salmonella typhimurium in mice [17].
  • The results indicate the presence of an rpoS- and phoP-independent pathway important to starvation- and stationary-phase-induced resistance to membrane-permeabilizing antimicrobial agents [18].
  • Transcriptional fusions to the Salmonella typhimurium genes sodCII and sitA were constructed using this method and shown to respond appropriately to mutations in the respective regulatory genes, rpoS and fur [19].
  • Insertions in several other genes, including such highly pleiotropic mutants as rpoS, polA, and hfq, were isolated with the same phenotypic screen, but they do not affect the beta-galactosidase activity of HemA-LacZ [20].

Analytical, diagnostic and therapeutic context of rpoS

  • The systemic humoral response induced by S. typhimurium rpoS, aroA and rpoS aroA vaccine candidates against S. typhimurium LPS was studied by ELISA [14].


  1. Avirulence of LT2 strains of Salmonella typhimurium results from a defective rpoS gene. Swords, W.E., Cannon, B.M., Benjamin, W.H. Infect. Immun. (1997) [Pubmed]
  2. Virulence and vaccine potential of Salmonella typhimurium mutants deficient in the expression of the RpoS (sigma S) regulon. Coynault, C., Robbe-Saule, V., Norel, F. Mol. Microbiol. (1996) [Pubmed]
  3. The alternative sigma factor katF (rpoS) regulates Salmonella virulence. Fang, F.C., Libby, S.J., Buchmeier, N.A., Loewen, P.C., Switala, J., Harwood, J., Guiney, D.G. Proc. Natl. Acad. Sci. U.S.A. (1992) [Pubmed]
  4. Essential roles of core starvation-stress response loci in carbon-starvation-inducible cross-resistance and hydrogen peroxide-inducible adaptive resistance to oxidative challenge in Salmonella typhimurium. Seymour, R.L., Mishra, P.V., Khan, M.A., Spector, M.P. Mol. Microbiol. (1996) [Pubmed]
  5. An altered rpoS allele contributes to the avirulence of Salmonella typhimurium LT2. Wilmes-Riesenberg, M.R., Foster, J.W., Curtiss, R. Infect. Immun. (1997) [Pubmed]
  6. Identification of sigma S-regulated genes in Salmonella typhimurium: complementary regulatory interactions between sigma S and cyclic AMP receptor protein. Fang, F.C., Chen, C.Y., Guiney, D.G., Xu, Y. J. Bacteriol. (1996) [Pubmed]
  7. Survival and filamentation of Salmonella enterica serovar enteritidis PT4 and Salmonella enterica serovar typhimurium DT104 at low water activity. Mattick, K.L., Jørgensen, F., Legan, J.D., Cole, M.B., Porter, J., Lappin-Scott, H.M., Humphrey, T.J. Appl. Environ. Microbiol. (2000) [Pubmed]
  8. The rpoS-dependent starvation-stress response locus stiA encodes a nitrate reductase (narZYWV) required for carbon-starvation-inducible thermotolerance and acid tolerance in Salmonella typhimurium. Spector, M.P., Garcia del Portillo, F., Bearson, S.M., Mahmud, A., Magut, M., Finlay, B.B., Dougan, G., Foster, J.W., Pallen, M.J. Microbiology (Reading, Engl.) (1999) [Pubmed]
  9. Acid shock induction of RpoS is mediated by the mouse virulence gene mviA of Salmonella typhimurium. Bearson, S.M., Benjamin, W.H., Swords, W.E., Foster, J.W. J. Bacteriol. (1996) [Pubmed]
  10. Invasiveness in chickens, stress resistance and RpoS status of wild-type Salmonella enterica subsp. enterica serovar typhimurium definitive type 104 and serovar enteritidis phage type 4 strains. Jørgensen, F., Leach, S., Wilde, S.J., Davies, A., Stewart, G.S., Humphrey, T. Microbiology (Reading, Engl.) (2000) [Pubmed]
  11. Role of sigma factor RpoS in initial stages of Salmonella typhimurium infection. Nickerson, C.A., Curtiss, R. Infect. Immun. (1997) [Pubmed]
  12. Expression of Salmonella typhimurium rpoS and rpoS-dependent genes in the intracellular environment of eukaryotic cells. Chen, C.Y., Eckmann, L., Libby, S.J., Fang, F.C., Okamoto, S., Kagnoff, M.F., Fierer, J., Guiney, D.G. Infect. Immun. (1996) [Pubmed]
  13. High levels of transcription factor RpoS (sigma S) in mviA mutants negatively affect 1,2-propanediol-dependent transcription of the cob/pdu regulon of Salmonella typhimurium LT2. Rondon, M.R., Escalante-Semerena, J.C. FEMS Microbiol. Lett. (1998) [Pubmed]
  14. Comparison of the abilities of Salmonella typhimurium rpoS, aroA and rpoS aroA strains to elicit humoral immune responses in BALB/c mice and to cause lethal infection in athymic BALB/c mice. Coynault, C., Norel, F. Microb. Pathog. (1999) [Pubmed]
  15. Intestinal colonisation-inhibition and virulence of Salmonella phoP, rpoS and ompC deletion mutants in chickens. Methner, U., Barrow, P.A., Gregorova, D., Rychlik, I. Vet. Microbiol. (2004) [Pubmed]
  16. Fis regulates transcriptional induction of RpoS in Salmonella enterica. Hirsch, M., Elliott, T. J. Bacteriol. (2005) [Pubmed]
  17. The live oral typhoid vaccine Ty21a is a rpoS mutant and is susceptible to various environmental stresses. Robbe-Saule, V., Coynault, C., Norel, F. FEMS Microbiol. Lett. (1995) [Pubmed]
  18. Starvation- and Stationary-phase-induced resistance to the antimicrobial peptide polymyxin B in Salmonella typhimurium is RpoS (sigma(S)) independent and occurs through both phoP-dependent and -independent pathways. McLeod, G.I., Spector, M.P. J. Bacteriol. (1996) [Pubmed]
  19. Construction of targeted single copy lac fusions using lambda Red and FLP-mediated site-specific recombination in bacteria. Ellermeier, C.D., Janakiraman, A., Slauch, J.M. Gene (2002) [Pubmed]
  20. Stabilization of a HemA-LacZ hybrid protein against proteolysis during carbon starvation in atp mutants of Salmonella typhimurium. Archer, C.D., Jin, J., Elliott, T. J. Bacteriol. (1996) [Pubmed]
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