Yersinia pseudotuberculosis Harbors a Type IV Pilus Gene Cluster that Contributes to Pathogenicity
Two features suggest that Y. pseudotuberculosis may have acquired the pil operon by horizontal gene transfer: (i) the pil locus is not uniformly present throughout the species; (ii) whereas the mean G+C% content of the Y. pseudotuberculosis genome is 47%, that of the pil operon is 50.8%. This value is very close to the G+C% content of the genomes of the type IV pilus-producing species E. coli and Salmonella (51–52%). This favors the view that Y. pseudotuberculosis, which occupies the same ecological niche as these two other enterobacteria, may have acquired the type IV pilus locus from one of these species by genetic exchange in the natural habitat. The two Salmonella pil operons have been found located either on a conjugative plasmid (Kim and Komano, 1997) or a large (118 kb) pathogenicity island (Zhang et al., 2000). Other type IVB pilus gene clusters, in enteropathogenic E. coli and V. cholerae, were also found to be harbored either on a plasmid (Girón et al., 199; Girón et al., 1994) or a pathogenicity island (Karolis et al., 1999). In Y. pseudotuberculosis 32777, in which the type IV pilus gene cluster has been discovered, no plasmid other than the virulence plasmid pYV was detected. Thus, given the scenarios in S. enterica, E. coli and V. cholerae, it is tempting to speculate that the Y. pseudotuberculosis pil operon could constitute a novel “adaptation-pathogenicity” island, unknown up until now, which in addition to the already described High Pathogenicity Island (HPI) (Buchrieser et al., 1999) contributes to the virulence of Y. pseudotuberculosis.
KeywordsPathogenicity Island Yersinia Pestis Strain MC1061 Aspartic Acid Protease Prepilin Peptidase
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