title: Identification of a novel Citrobacter rodentium type III secreted protein, EspI, and roles of this and other secreted proteins in infection.
abstract: Citrobacter rodentium is a member of a group of pathogens that colonize the lumen of the host gastrointestinal tract via attaching and effacing (A/E) lesion formation. C. rodentium, which causes transmissible colonic hyperplasia in mice, is used as an in vivo model system for the clinically significant A/E pathogens enterohemorrhagic and enteropathogenic Escherichia coli. These bacteria all contain a pathogenicity island called the locus of enterocyte effacement (LEE), which encodes a type III secretion system that is designed to deliver effector proteins into eukaryotic host cells. These effectors are involved in the subversion of host eukaryotic cell functions to the benefit of the bacterium. In this study we used mutant strains to determine the effects of the C. rodentium LEE-encoded effectors EspF, EspG, EspH, and Map on virulence in the mouse model. In addition, we identified a novel secreted protein, EspI encoded outside the LEE, whose secretion is also dependent on a functional type III secretion system. Mutant strains with each of the effectors investigated were found to be outcompeted by wild-type bacteria in mixed-infection experiments in vivo, although the effects of EspF and EspH were only subtle. In single-infection experiments, we found that EspF, EspG, and EspH are not required for efficient colonization of the mouse colon or for the production of hyperplasia. In contrast, strains producing EspI and Map had significant colonization defects and resulted in dramatically reduced levels of hyperplasia, and they exhibited very different growth dynamics in mice than the wild-type strain exhibited.
authors.affiliation: Centre for Molecular Microbiology and Infection, Department of Biological Sciences, Imperial College, London SW7 2AZ, United Kingdom.
authors.forename: Rosanna
authors.initials: R
authors.lastname: Mundy
authors.forename: Liljana
authors.initials: L
authors.lastname: Petrovska
authors.forename: Katherine
authors.initials: K
authors.lastname: Smollett
authors.forename: Nandi
authors.initials: N
authors.lastname: Simpson
authors.forename: Rebecca K
authors.initials: RK
authors.lastname: Wilson
authors.forename: Jun
authors.initials: J
authors.lastname: Yu
authors.forename: Xuanlin
authors.initials: X
authors.lastname: Tu
authors.forename: Ilan
authors.initials: I
authors.lastname: Rosenshine
authors.forename: Simon
authors.initials: S
authors.lastname: Clare
authors.forename: Gordon
authors.initials: G
authors.lastname: Dougan
authors.forename: Gad
authors.initials: G
authors.lastname: Frankel
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D044082:Citrobacter rodentium / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D003106:Colon / Q000382:microbiology / Q000473:pathology; D004756:Enterobacteriaceae Infections / Q000382:microbiology / Q000473:pathology; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008969:Molecular Sequence Data; D009154:Mutation; D017422:Sequence Analysis, DNA; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; C484701:EspI protein, Citrobacter rodentium