The major virulence factors of Yersinia pestis, pgm locus and plasmid pCD1-encoded V antigen (LcrV), have a high degree of homology with little intraspecific differences in their structure. Molecular typing is a great source... [ view full abstract ]
The major virulence factors of Yersinia pestis, pgm locus and plasmid pCD1-encoded V antigen (LcrV), have a high degree of homology with little intraspecific differences in their structure. Molecular typing is a great source tracker for Y. pestis and also determines its distribution. In this study, we compared the structure of 102Kb unstable pgm locus and its flanking regions and examined sequence variability of LcrV of an epidemic and non-epidemic Y. pestis isolates from Georgia and neighboring FSU countries from the National Center for Disease Control and Public Health’s (NCDC’s) collection.
Whole-genome sequencing of 11 Y. pestis isolates were performed using a combination of Illumina and 454 technologies (Roche). Isolates were from the following regions: Georgia (n=6), Armenia (n=2), Russia (n=1), Azerbaijan (n=1), and Kyrgyzstan (n=1). The complete sequences of pgm locus and its flanking regions and the LcrV gene were aligned and compared using CLC Genomics Workbench software package (v8.5 CLC bio).
The study revealed that the whole pgm locus is deleted in strains form Azerbaijan and Russia. The porin gene (ompY), which is adjacent to the pgm region, is usually damaged in highly virulent Y. pestis strains, and is interrupted by insertion sequence IS100 in Kyrgyz strain C790. This gene is intact in Georgian and Armenian Pestoides strains, comparable to Y. pestis Angola strain (pestoide biovar Microtus str 91001), and some Yersinia pseudotuberculosis strains. In the hutG gene, which is adjacent to ompY porin, a copy of IS100, was detected in an opposite direction as also found only in Pestoides F and G. In these strains, deletion of the pgm region by flanked IS100 is impossible since IS100 is integrated in the hutG gene in an opposite orientation that correlates with the (pgm+) phenotype on CRA plates of Georgian and Armenian strains. Sequence variation among V antigen was also observed. Alignment of amino acid sequences of LcrV gene of Y. pestis strains from different foci showed that nine strains had sequences identical to the previously reported predominant LcrV sequence (CO92, KIM, and Pestoides G) encoding 326 amino acids. Two Armenian strains have a deletion at the C-terminus of the protein and encoding 324 amino acids identical to LcrV sequence of Pestoides F and biovar Microtus str. 91001.
The present study demonstrated that unlike the Y. pestis strains of main subspecies Georgian/Armenian strains have intact porin gene and inverted IS100 integrated into the hutG, which might be responsible for stabilizing the pgm region as a homologous recombination, which occurred in direct copies of IS100. Although LcrV is a conserved gene, our study showed that LcrV displayed variation in size and amino acid sequence among very closely related strains such as Georgian and Armenian Pestoides strains. Influence of LcrV sequence polymorphism on the virulence of these strains needs further investigation.
Sequencing applications for metagenomics, transcriptomics, diagnostics, and biosurveillanc
