title: Salmonella paratyphi C: genetic divergence from Salmonella choleraesuis and pathogenic convergence with Salmonella typhi.
abstract: BACKGROUND
  Although over 1400 Salmonella serovars cause usually self-limited gastroenteritis in humans, a few, e.g., Salmonella typhi and S. paratyphi C, cause typhoid, a potentially fatal systemic infection. It is not known whether the typhoid agents have evolved from a common ancestor (by divergent processes) or acquired similar pathogenic traits independently (by convergent processes). Comparison of different typhoid agents with non-typhoidal Salmonella lineages will provide excellent models for studies on how similar pathogens might have evolved.
  
  
  RESULTS
  We sequenced a strain of S. paratyphi C, RKS4594, and compared it with previously sequenced Salmonella strains. RKS4594 contains a chromosome of 4,833,080 bp and a plasmid of 55,414 bp. We predicted 4,640 intact coding sequences (4,578 in the chromosome and 62 in the plasmid) and 152 pseudogenes (149 in the chromosome and 3 in the plasmid). RKS4594 shares as many as 4346 of the 4,640 genes with a strain of S. choleraesuis, which is primarily a swine pathogen, but only 4008 genes with another human-adapted typhoid agent, S. typhi. Comparison of 3691 genes shared by all six sequenced Salmonella strains placed S. paratyphi C and S. choleraesuis together at one end, and S. typhi at the opposite end, of the phylogenetic tree, demonstrating separate ancestries of the human-adapted typhoid agents. S. paratyphi C seemed to have suffered enormous selection pressures during its adaptation to man as suggested by the differential nucleotide substitutions and different sets of pseudogenes, between S. paratyphi C and S. choleraesuis.
  
  
  CONCLUSIONS
  S. paratyphi C does not share a common ancestor with other human-adapted typhoid agents, supporting the convergent evolution model of the typhoid agents. S. paratyphi C has diverged from a common ancestor with S. choleraesuis by accumulating genomic novelty during adaptation to man.
authors.affiliation: Genomics Research Center, Harbin Medical University, Harbin, China.
authors.forename: Wei-Qiao
authors.initials: WQ
authors.lastname: Liu
authors.forename: Ye
authors.initials: Y
authors.lastname: Feng
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.forename: Qing-Hua
authors.initials: QH
authors.lastname: Zou
authors.forename: Fang
authors.initials: F
authors.lastname: Chen
authors.forename: Ji-Tao
authors.initials: JT
authors.lastname: Guo
authors.forename: Yi-Hong
authors.initials: YH
authors.lastname: Peng
authors.forename: Yan
authors.initials: Y
authors.lastname: Jin
authors.forename: Yong-Guo
authors.initials: YG
authors.lastname: Li
authors.forename: Song-Nian
authors.initials: SN
authors.lastname: Hu
authors.forename: Randal N
authors.initials: RN
authors.lastname: Johnston
authors.forename: Gui-Rong
authors.initials: GR
authors.lastname: Liu
authors.forename: Shu-Lin
authors.initials: SL
authors.lastname: Liu
mesh_terms: D000818:Animals; D005798:Genes, Bacterial / Q000235:genetics*; D016680:Genome, Bacterial; D006801:Humans; D010802:Phylogeny; D012475:Salmonella / Q000235:genetics*; D012476:Salmonella arizonae / Q000235:genetics; D012479:Salmonella paratyphi C / Q000235:genetics; D012485:Salmonella typhi / Q000235:genetics; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D013552:Swine