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Based on the results of computer analysis of nucleotide sequences in strains Yersinia pestis and Y. pseudotuberculosis recorded in the files of NCBI GenBank database, differences between genes argA, aroG, aroF, thiH, and thiG of strain Pestoides F (subspecies caucasica) were found, compared to other strains of plaque agent and pseudotuberculosis microbe. Using PCR with calculated primers and the method of sequence analysis, the structure of variable regions of these genes was studied in 96 natural Y. pestis and Y. pseudotuberculosis strains. It was shown that all examined strains of subspecies caucasica, unlike strains of plague-causing agent of other subspecies and pseudotubercolosis microbe, had identical mutations in genes argA (integration of the insertion sequence IS100), aroG (insertion of ten nucleotides), aroF (inserion of IS100), thiH (insertion of nucleotide T), and thiG (deletion of 13 nucleotides). These mutations are the reason for the absence in strains belonging to this subspecies of the ability to synthesize arginine, phenylalanine, tyrosine, and vitamin B1 (thiamine), and cause their auxotrophy for these growth factors.

Comparative molecular-genetic analysis of clinical Vibrio cholerae eltor biovariant strains isolated in Russia during various years.Microbiological and biochemical methods were used for studies of 25 clinical strains of classic and eltor biovariant cholera, PCR testing and sequencing of various genes was also performed.Phenotypic and genetic analysis of clinical V. cholerae strains isolated in Russia during 7th cholera pandemic has confirmed that they belong to biovariant eltor. PCR testing of 21 isolates obtained from patients in 1970 - 2010 has shown that epidemic complications in Russia from 1993 were caused by altered V. cholerae biovariant eltor. Presence of classic cholera biovariant ctxB coding gene in cholera toxin coding CTX prophage is the genetic alteration of these variants, ctxB sequencing in altered variants has confirmed PCR data and shown 2 ctxB gene alleles (ctxB1 and ctxB7). Altered variants produced significantly more cholera toxin than typical strains.In 1970 - 2010 67.6% of clinical isolates were altered V. cholera biovariant eltor variants. These new variants were genetically diverse. Alteration of cholera eltor biovariant genome caused toxigenicity increase.

Structural and functional organization of genes responsible for biosynthesis of amino acid methionine, which plays a leading role in cellular metabolism of bacteria, was studied in 24 natural Yersinia pestis strains of the major and minor subspecies from various natural plague foci located in the territory of Russian Federation and neighbouring foreign countries, and also in Y. pestis and Y. pseudotuberculosis strains recorded in the files of NCBI GenBank database. Conservatism of genes metA, metB, metC, metE, and metH as well as regulatory genes metR and metJ involved in biosynthesis of this amino acid was established. Sequencing of the variable locus of gene metB in natural Y. pestis strains of major and minor subspecies revealed that the reason for the methionine dependence of strains belonging to the major subspecies is a deletion of a single nucleotide (-G) in the 988 position from the beginning of the gene, whereas this dependence in strains belonging to subspecies hissarica results from the appearance of a single nucleotide (+G) insertion in the 989 position of gene metB. These mutations are absent in strains of the caucasica, altaica, and ulegeica subspecies of the plague agent and in strains of pseudotuberculosis microbe, which correlates with their capacity for methionine biosynthesis.

A study of the structural and regulatory genes, determining rhamnose fermentation, that are located in the rha locus of the chromosome of Yersinia pestis main and non-main subspecies and of Yersinia pseudotuberculosis of serogroups I-III was performed. The nucleotide sequence of Y. pestis main subspecies differs substantially from those of non-main subspecies and Y. pseudotuberculosis by the presence of a nucleotide substitution in 671 bp location of rhaS gene resulting presumably in the Y. pestis non-main subsp inability to utilize rhamnose. This results in incapability of Y. pestis non-main subspecies to utilize rhamnose. Other nucleotide substitutions found in Y. pestis non-main subspecies strains influence only upon expression efficiency of this diagnostic criterion.

The evolution of the genome of the pathogenic agent of the seventh cholera pandemia Vibrio cholerae eltor biovariant was thought to occur by acquiring not only structural genes of virulence but also regulatory systems as a result of horizontal transfer events. The polymerase chain reaction revealed the presence of the following regulatory genes that control the virulence gene expression in the chromosome of pre-pandemic and pandemic strains of cholera vibrios eltor: toxR, toxT, tcpP, tcpH, luxS, luxO, crp, vicH, pepA. The avirulent V. cholerae strain ATCC14033 isolated in 1910 (hypothetical predecessor of the cholera eltor agent) was shown to be lacking the regulatory genes toxT, tcpP, tcpHlocalized in the pathogenicity island VPI-1, and to be capable of realizing positive control over the expression of the virulence genes involved in the ToxR regulon. The virulent strains isolated from cholera patients during the local cholera outbreak in Indonesia in 1937 did not differ from the strains that caused cholera eltor pandemic in 1961. The strains had identical content of the regulatory genes tested. Only one strain of the four isolates studied contained no tcpPgene. Two key regulatory genes, toxR and toxT, were sequenced in all the isolates. The toxR nucleotide sequence of three pre-pandemic strains was shown to be indistinguishable from that of the pandemic isolates. On the other hand, the clinical strain MAK757 isolated prior to the emergence of the epidemic demonstrated an altered nucleotide sequence in its toxR gene. Experiments with the intra-intestinal challenge of suckling rabbits were indicative of similar virulence levels for the pre-pandemic and pandemic clinical strains. These results may serve as the evidence of the in vivo activity of the pre-pandemic strains of the toxT, tcpH, and tcpP positive regulatory genes that acquired in V. cholerae during the evolutionary process.