STRUCTURAL ORGANIZATION OF PORIN GENES (INTACT AND DISRUPTED BY IS 100) BORDERING THE PGM LOCUS OF THE YERSINIA PESTIS AND YERSINIA PSEUDOTUBERCULOSIS STRAINS.

In highly virulent strains of Yersinia pestis, the porin gene border- ing pigmentation (pgm) locus was observed to be usually broken by IS100. In this case, the pgm locus that carries virulence genes (high pathogenicity island) and biofilm formation genes (hms operon) is flanked by direct copies of IS100, which can cause its destabilization. We studied the prevalence of the intact and dis- rupted porin genes among 240 strains of Y. pestis from 39 natural centers in Russia and abroad, and 68 strains of Yersinia pseudotuberculosis from different geographical regions. The majority of the highly virulent Y. pestis strains and some phylogenetic lines of Y. pseudotuberculosis 0:1 serotype contain disrupted porin genes. At the same time, deletion of the pgm locus by flanking IS100 in Y pseudotuberculosis is impossible, because IS100 is integrated in the porin gene in the reverse orientation as compared to Y pestis. The porin genes are intact in all Y pestis strains with low epidemic importance and some phylogenetic lines of highly virulent Y pestis strains from some desert foci and Caspian sandy focus, as well as most strains of Y pseudotuberculosis 0:1 serotype. Less virulent strains of Y pseudotuberculosis 0:3 serotype revealed extensive deletion, which included the porin gene and a portion of the gene astE. The nucleotide sequence of the porin genes in Y pestis and Y pseudotuberculosis strains from different geographical regions are identical. Three alleles of the porin gene differ solely by the site of integration and orientation of IS 100 or by the lack of integration. The nucleotide sequence of IS 100, embedded in the porin gene of Yersinia, has minor differences only in two Y pestis strains isolated in America. Low frequency of Hms- mutations correlates with the intact condition of the porin gene in Y pestis. This correlation is absent in Y pseudotuberculosis.

[Analysis of the Nucleotide Sequence of a Cryptic Plasmid from Yersinia pestis Strains in the Central Caucasian High-Mountain Plague Focus].

An analysis of a 5.4-kbp cryptic plasmid detected in the course of whole-genome sequencing of the Yersinia pestis medieval biovar isolated in the Russian Central Caucasian high-mountain plague focus was performed. The identification of the nucleotide sequence of this cryptic plasmid and its structural and functional analysis revealed that it contained eight open reading frames, among which the following genes were identified: the rep gene of a replication protein, the virB6 gene of a type-IV secretion system inner membrane protein, the virB5gene of the type-IV secretion system minor pilin, and a number of genes probably associated with secretion and transport. A general analysis of the pCKF plasmid DNA showed that the adenine content was 28.34%, the cytosine content was 20.5%, the guanine content was 17.87%, and that of thymine was 33.28%, while the total G+C content appeared to be 38.38%. The G+C content of the chromosome of the Y pestis strain C-627 is 47.6%, which indicates that the pCKF plasmid was obtained from a microorganism equally-phylogenetically distant from the Yersinia bacteria andany other bacteria from the Enterobacteriaceae family. A comparison of the amino acid sequences.of hypothetical proteins encoded by pCKF plasmid with analogous proteins encoded by other bacteria was carried out. The possible contribution of the pCKF plasmid to the maintenance of the most ancient known phylogenetic line of Y. pestis medieval biovar, 2.MEDO, was discussed.

[A study on the taxonomy of soil amoebas from Caspian plague foci based on an analysis of ribosomal operon sequences].

The results of a study on the taxonomy and quantitative abundance of free-living amoebas in soil samples from the Russian plague foci of the northwestern Caspian steppe, the Caspian sand, and the Volga-Ural steppe are presented. Amoebas of the Willaertia and Hartmanella genera, as well as representatives of myxomycetes, were isolated from samples. From these, amoebas of the Acanthamoeba genus predominated and could be as abundantas 300000 cells per 1 g of soil. Sequencing of the 18S rRNA gene region showed that Acanthamoeba from the Volga-Ural steppe focus belonged to the A. castellanii species. Phylogenetic analysis confirmed that amoebas from two other Caspian foci belonged to the species of Acanthamoeba spp.