title: Role of RpoS in the virulence of Citrobacter rodentium.
abstract: Citrobacter rodentium is a mouse enteropathogen that is closely related to Escherichia coli and causes severe colonic hyperplasia and bloody diarrhea. C. rodentium infection requires expression of genes of the locus of enterocyte effacement (LEE) pathogenicity island, which simulates infection by enteropathogenic E. coli and enterohemorrhagic E. coli in the human intestine, providing an effective model for studying enteropathogenesis. In this study we investigated the role of RpoS, the stationary phase sigma factor, in virulence in C. rodentium. Sequence analysis showed that the rpoS gene is highly conserved in C. rodentium and E. coli, exhibiting 92% identity. RpoS was critical for survival under heat shock conditions and during exposure to H(2)O(2) and positively regulated the expression of catalase KatE (HPII). The development of the RDAR (red dry and rough) morphotype, an important virulence trait in E. coli, was also mediated by RpoS in C. rodentium. Unlike E. coli, C. rodentium grew well in the mouse colon, and the wild-type strain colonized significantly better than rpoS mutants. However, a mutation in rpoS conferred a competitive growth advantage over the wild type both in vitro in Luria-Bertani medium and in vivo in the mouse colon. Survival analysis showed that the virulence of an rpoS mutant was attenuated. The expression of genes on the LEE pathogenicity island, which are essential for colonization and virulence, was reduced in the rpoS mutant. In conclusion, RpoS is important for the stress response and is required for full virulence in C. rodentium.
authors.affiliation: Department of Biology, Life Sciences Building, Rm. 433, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada.
authors.forename: Tao
authors.initials: T
authors.lastname: Dong
authors.forename: Brian K
authors.initials: BK
authors.lastname: Coombes
authors.forename: Herb E
authors.initials: HE
authors.lastname: Schellhorn
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D044082:Citrobacter rodentium / Q000187:drug effects / Q000235:genetics / Q000472:pathogenicity* / Q000528:radiation effects; D003106:Colon / Q000382:microbiology; D015169:Colony Count, Microbial; D017124:Conserved Sequence; D004926:Escherichia coli / Q000235:genetics; D006358:Hot Temperature; D006861:Hydrogen Peroxide / Q000494:pharmacology; D050296:Microbial Viability; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D012808:Sigma Factor / Q000235:genetics / Q000502:physiology*; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D016877:Oxidants; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; D006861:Hydrogen Peroxide