title: The Citrobacter rodentium genome sequence reveals convergent evolution with human pathogenic Escherichia coli.
abstract: Citrobacter rodentium (formally Citrobacter freundii biotype 4280) is a highly infectious pathogen that causes colitis and transmissible colonic hyperplasia in mice. In common with enteropathogenic and enterohemorrhagic Escherichia coli (EPEC and EHEC, respectively), C. rodentium exploits a type III secretion system (T3SS) to induce attaching and effacing (A/E) lesions that are essential for virulence. Here, we report the fully annotated genome sequence of the 5.3-Mb chromosome and four plasmids harbored by C. rodentium strain ICC168. The genome sequence revealed key information about the phylogeny of C. rodentium and identified 1,585 C. rodentium-specific (without orthologues in EPEC or EHEC) coding sequences, 10 prophage-like regions, and 17 genomic islands, including the locus for enterocyte effacement (LEE) region, which encodes a T3SS and effector proteins. Among the 29 T3SS effectors found in C. rodentium are all 22 of the core effectors of EPEC strain E2348/69. In addition, we identified a novel C. rodentium effector, named EspS. C. rodentium harbors two type VI secretion systems (T6SS) (CTS1 and CTS2), while EHEC contains only one T6SS (EHS). Our analysis suggests that C. rodentium and EPEC/EHEC have converged on a common host infection strategy through access to a common pool of mobile DNA and that C. rodentium has lost gene functions associated with a previous pathogenic niche.
authors.affiliation: The Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SA, UK.
authors.forename: Nicola K
authors.initials: NK
authors.lastname: Petty
authors.forename: Richard
authors.initials: R
authors.lastname: Bulgin
authors.forename: Valerie F
authors.initials: VF
authors.lastname: Crepin
authors.forename: Ana M
authors.initials: AM
authors.lastname: Cerdeño-Tárraga
authors.forename: Gunnar N
authors.initials: GN
authors.lastname: Schroeder
authors.forename: Michael A
authors.initials: MA
authors.lastname: Quail
authors.forename: Nicola
authors.initials: N
authors.lastname: Lennard
authors.forename: Craig
authors.initials: C
authors.lastname: Corton
authors.forename: Andrew
authors.initials: A
authors.lastname: Barron
authors.forename: Louise
authors.initials: L
authors.lastname: Clark
authors.forename: Ana L
authors.initials: AL
authors.lastname: Toribio
authors.forename: Julian
authors.initials: J
authors.lastname: Parkhill
authors.forename: Gordon
authors.initials: G
authors.lastname: Dougan
authors.forename: Gad
authors.initials: G
authors.lastname: Frankel
authors.forename: Nicholas R
authors.initials: NR
authors.lastname: Thomson
mesh_terms: D000818:Animals; D044082:Citrobacter rodentium / Q000145:classification / Q000235:genetics*; D019295:Computational Biology; D004926:Escherichia coli / Q000235:genetics*; D019143:Evolution, Molecular; D016680:Genome, Bacterial / Q000235:genetics*; D006801:Humans; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D010802:Phylogeny