[Structural-functional characteristics of Yersinia pseudotuberculosis plasmid pVM82]. / Strukturno-funktsional'naia kharakteristika plazmidy Yersinia pseudotuberculosis pVM82.

The restriction map of Yersinia pseudotuberculosis plasmid pVM82 was established using the "chromosome walking" method. According to transpositional mutagenesis, the plasmid pVM82 appeared to be conjugative and was able to be transmitted from Y. pseudotuberculosis to the E. coli K-12 cells.

[Study of polymorphism of strains of Vibrio cholerae of various origins using a method of genomic fingerprinting]. / Izuchenie polimorfizma shtammov kholernogo vibriona raznogo proiskhozhdeniia metodom genomnoi daktiloskopii.

Population of atoxigenic Eltor vibrios (vct-) isolated from open water has been shown to be heterogeneous by the genomic fingerprinting technique. Epidemically dangerous strains (vct+) containing the gene coding for cholera toxin have similar hybridization profile independent of time and place of their isolation. The clonal formation of vct+ strains and the absence of vct----vct+ transition of strains under natural conditions are discussed.

[Analysis of the plasmid composition of Yersinia pseudotuberculosis strains and its use for typing pseudotuberculosis pathogens]. / Analiz plazmidnogo sostava shtammov Yersinia pseudotuberculosis i ego primenenie dliia tipirovaniia vozbutiteliia pseevdotuberkuleza.

Electrophoresis in agarose gel has been used to study the plasmid spectra of 854 Yersinia pseudotuberculosis strains isolated from different sources. The plasmids found in the microbial strains are represented by the elements with molecular masses 82; 57; 45; 5.5; 4.4; 3.5; 2.7; 2.4; 2.3 Md. The variable spectra of plasmids is peculiar only for serovar I of Yersinia pseudotuberculosis. Plasmids p45 and p82 are classified as the main, while other plasmids as auxiliary ones. In accord with the classification all plasmid containing strains are divided into 8 plasmid strains. Using the proposed method for intraspecific typing of Yersinia pseudotuberculosis permits one to perfect the epidemiological analysis of pseudotuberculosis infection and make concrete the direction of prophylactic and antiepidemic measures.

[Integration with the chromosome--an alternative state of calcium-dependency plasmids in Yersinia]. / Integratsiia s khromosomoi--al'ternativnoe sostoianie plazmid kal'tsiizavisimosti u vozbuditelei iersiniozov.

Using the technique of the genes probes the naturally occuring strains Y. pseudotuberculosis and Y. enterocolitica of epidemiological importance were shown to contain pCad plasmid integrated with the chromosome. The strains having integrated plasmid express all pathogenicity determinants necessary for realization of infectious process.

[A new pathogenic trait encoded by Yersinia pseudotuberculosis pVM82 plasmid]. / Novyi priznak patogennosti, kodiruemyi plazmidoi pVM82 Yersinia pseudotuberculosis.

The strains of Yersinia pseudotuberculosis isolated from patients in the course of outbreaks of infection (epidemic strains) were found to possess at least two plasmids with molecular masses of 45 and 82 MD. In contrast, the strains obtained in sporadic cases harbored different sets of plasmids, but never the 82 MD plasmids. These plasmids designated pVM82 and isolated from strains of different geographic regions of the country were identical. pVM82 have no homology with Y. pestis plasmids of the similar size coding for the FraI antigen. The pVM82 DNA was found to be composed of the 57 MD plasmid DNA and the 25 MD fragment of Y. pseudotuberculosis DNA. Using Western blot hybridization technique it was shown that the presence of pVM82 suppressed formation of antibody against some major antigenic determinants of Y. pseudotuberculosis. Immunosuppression took place when the animals were infected with bacteria grown below 20 but not at 37 degrees C. The 57 MD plasmid failed to produce immunosuppression. It was concluded that the 25 MD fragment of pFN82 encoded a novel pathogenic factor responsible for immunosuppression.

[The role of the RS1 sequence of Vibrio cholerae in the amplification of a segment of plasmid DNA carrying the tetracycline resistance gene and cholera toxin genes]. / Rol' RS1-posledovatel'nosti kholernogo vibriona v amplifikatsii segmenta plazmidnoi DNK, nesushchego gen rezistentnosti k tetratsiklinu i geny kholernogo toksina.

The clones with 4 to 30-fold increased level of tetracycline resistance (TcR) were selected from the strain of Escherichia coli K-12 carrying the pCO107 plasmid. The plasmid is the cointegrate formed from the plasmids pOX38 (F-derivative) and pCT105 (pBR322-derivative carrying the vct operon of Vibrio cholerae eltor and the RSI sequence). pCO107 contains RSI at the junctions of two plasmid genomes. Using restriction analysis and Southern blot hybridization technique it was shown that increased tetracycline resistance is accompanied by amplification of the pCT105 segment of pCO107 and depends upon the presence of direct repeats of flanking RSI. Amplification of the pCT105 also resulted in increased production of the cholerae toxin (CT).

[The use of the gene hybridization method for the identification of epidemiologically dangerous strains of cholera vibrios]. / Primenenie metoda gennogo zondirovaniia dlia vyiavleniia épidemicheski opasnykh shtammov kholernykh vibrionov.

Using the labeled DNA fragments containing the genes for cholera toxin the strains of cholera vibrios were studied for the presence of cholera toxin genes. Vibrio cholerae strains isolated from natural water reservoirs under the favourable epidemic situation do not contain the cholera toxin genes. The DNA hybridization method was compared with other methods used in research and practical work for estimation of epidemic importance of cholera vibrios.

[Construction of recombinant plasmids encoding the biosynthesis of the beta-subunit of cholera toxin]. / Konstruirovanie rekombinantnykh plazmid, kodiruiushchikh biosintez beta-sub''edinitsy kholernogo toksina.

The structure of the cholera toxin operon and the location of A and B toxin subunits have been studied by the Southern blot hybridization on filters. The gene coding for the synthesis of the cholera toxin B-subunit has been cloned in the vector plasmid pBR322. The structural gene of A-subunit has been partially deleted by the restriction endonuclease Bal31 digestion. The size of the 250 b. p. deletion has been defined by electron microscopy. The production of the cholera toxin B-subunit in Escherichia coli K12 cells has been studied.