Diversity of CRISPR loci in <i>Yersinia pseudotuberculosis</i> strains and their association with pathogenicity factors

Introduction. Heterogeneous microbial populations exist in the nature due to exchange of genetic material containing in extrachromosomal and transposable elements. Structures controlling horizontal gene transfer may affect development of pathogen genetic variants. The aim of the study is to analyze molecular genetic characteristics of CRISPR-loci in Yersinia pseudotuberculosis strains circulating in Russia and their association with pathogenicity factors. Materials and methods. We studied 56 strains of Y. pseudotuberculosis isolated from different sources in Russia during 19352014 from various sources in different regions of Russian Federation and in other countries. DNA fragments with CRISPR-loci were isolated and amplified by PCR, and subjected to Sanger sequencing. PCR was used to determine chromosomal genes of superantigen ypmA/C, pathogenicity islands HPI, YAPI, and plasmids pYV and pVM82. Results. Analysis of CRISPR-loci in Y. pseudotuberculosis showed that spacer content varies in strains depending on serotype, set of pathogenicity factors, and isolation place. The most variable loci are YP1 and YP3, locus YP2 is homogeneous. Locus YP1 varies in strains that differ by presence of plasmid pVM82, while content of locus YP3 depends on presence of plasmid pVM82 and adhesion pathogenicity island YAPI. Conclusion. Strains of Y. pseudotuberculosis circulating in Russia have a huge diversity of pathogenicity factors and CRISPR spacer content. Most of Russian strains differ by molecular markers from strains isolated in other countries. High variability is defined by ability to get new genetic elements in horizontal gene transfer. In bacteria, CRISPR-Cas system provides immunity against mobile genetic elements and can participate in formation of Y. pseudotuberculosis pathogenic potential.