The 102-kilobase pgm locus of Yersinia pestis: Sequence analysis and comparison of selected regions among different Yersinia pestis and Yersinia pseudotuberculosis strains

We report the complete 119,443-bp sequence of the pgm locus from Yersinia p estis and its flanking regions, Sequence analysis confirms that the 102-kb unstable pgm locus is composed of two distinct parts: the pigmentation segm ent and a high-pathogenicity island (HPI) which carries virulence genes inv olved in iron acquisition (yersiniabactin biosynthetic gene cluster), Withi n the HPI, three genes coding for proteins related to phage proteins were u ncovered. They are located at both extremities indicating that the entire H PI was acquired en bloc by phage-mediated horizontal transfer. We identifie d, within the pigmentation segment, two novel loci that may be involved in virulence: a fimbriae gene duster and a locus probably encoding a two compo nent regulatory system similar to the BvgAS regulatory system of Bordetella pertussis. Three genes containing frameshift mutations and two genes inter rupted by insertion element insertion were found within this region, To inv estigate diversity among different Y. pestis and Yersinia pseudotuberculosi s strains, the sequence of selected regions of the pgm locus and flanking r egions were compared from 20 different Y. pestis and 10 Y, pseudotuberculos is strains. The results showed that the genes interrupted in Y. pestis are intact in Y, pseudotuberculosis. However, one of these mutations, in the bv gS homologue, is only present in Y. pestis strains of biovar Orientalis and not in those of the biovars Antiqua and Medievalis, The results obtained b y analysis of variable positions in the sequence are in accordance with his torical records, confirming that biovar Orientalis is the most recent linea ge, Furthermore, sequence comparisons among 29 Yersinia strains suggest tha t Y. pestis is a recently emerged pathogen that is probably entering the in itial phase of reductive evolution.