[High homology of plasmids carrying class II restriction modification systems, EcoRV isoschizomers, and their prevalence in natural Escherichia coli strains]. / Vysokaia gomologiia plasmid, nesushchikh geny sistemy restriktsii-modifikatsii II klassa--izoshizomerov EcoRV, i ikh rasprostranenie v prirodnykh shtammakh Echerichia coli.

Screening of 660 clinical Enterbacteriaceae strains from the collection of L. V. Gromashevsky Kiev Institute of Epidemiology and Infectious Diseases for specific endonuclear activity revealed site-specific endonucleases, EcoRV isoschizomers in 6 E. coli strains. Genes coding for endonucleases and methyltransferases were localized on small (6.2 kb) multicopy Hsd+ plasmids. All plasmids were successfully transferred in laboratory strain E. coli K802. Restriction analysis and subcloning showed no differences in the structural and functional organization of studied plasmids and a previously revealed pLB1 plasmid [3,10], this reflecting their high homology, if not identity. These data allow us to propose effective horizontal transfer of EcoRV plasmids among natural E. coli isolates in the region studied.

[Novel isoschizomers of restriction endonucleases from Pseudomonas aeruginosa strains]. / Novye izoshizomery restriktsionnykh éndonukleaz v shtammakh Pseudomonas aeruginosa.

Testing of Pseudomonas aeruginosa strains from the collection of the L. V. Gromashevsky Institute of Epidemiology and Infectious Diseases (Kiev) for specific endonucleases resulted in isolation of five class II restriction endonucleases, which were partially purified and their recognition targets were determined. Two of these endonucleases, Pae2kI and Pae18kI, are isoschizomers of Bg1II (5'-AGACTC-3'). Pae5kI and Pae14kI recognize the 5'-CCGC/GG-3' sequence and are therefore true isoschizomers of SacII. Hence, Pae17kI is an isoschizomer of PvuII and cleaves the DNA within the recognition sequence 5'-CAG/CTG-3'. Bg1II and PvuII are for the first time detected in Pseudomonas aeruginosa.

[Restriction system--type II modification in Enterobacter cloacae strains]. / Sistemy restriktsii--modifikatsii II tipa v shtammakh Enterobacter cloacae.

Various clinical strains of Enterobacter cloacae have been examined for the presence of site-specific endonuclease activities. Restriction endonucleases of class II have been isolated from six strains. Recognition sequences for all of these endonucleases were determined and the cleavage sites were identified for two of them. The enzymes prove to be isoschizomers of EcoRII and PstI. Restriction endonucleases Ecl2zI and Ecl37kI recognise the nucleotide sequences CTGA/G and are true isoschizomers of PstI. The genes for Ecl54kI and Ecl57kI restriction-modification systems (isoschizomers of EcoRII) were found to be located on the IncN group plasmids, whereas the genes for Ecl2zI and Ecl99kI seem to be located on the chromosomes of host cells.

[Plasmid localization and cloning of restriction modification genes from Citrobacter freundii 4111 strain]. / Plazmidnaia lokalizatsiia i klonirovanie genov sistemy restriktsii-modifikatsii iz shtamma Citrobacter freundii 4111.

Over 60 producing strains of restriction endonucleases type II have been found among 500 different strains, mostly Enterobacteriaceae. The strain Citrobacter freundii 4111 produces restriction endonuclease CfrBI, a new isoschisomer of StyI. The genes of the restriction-modification system CfrBI were located on the multicopy plasmid pZE8 containing the Co1E1-type replicon and cloned to E. coli K802. The deletion variant of 3.2-kb pZE8 which contains intact restriction-modification and a DNA fragment responsible for autonomous plasmid replication was selected among the recombinant plasmids. The strain with higher R. CfrBI production (at least 10,000,000 U/g cells, which is 500-fold higher than the wild strain) was constructed.

[Mapping of the genetic determinant controlling Salmonella K-antigen synthesis. II. Nonmotile mutants of Salmonella typhimurium]. / Kartirovanie geneticheskogo determinanta, kontroliruiushchego sintez K-antigena sal'monell. Soobshchenie II. Izuchenie nepodvizhnykh mutantov Salmonella typhimurium.

According to the preliminary data, S. typhimurium K-antigen is located in the area of minutes 40-44 on the Salmonella chromosome map. The formation of nonmotile mutants from motile Salmonella strains was induced by the action of nitrosoguanidine. Two main groups of mutants differing in their reaction of agglutination with H- and K-antisera were obtained: Mot-H-K- (motA or motB mutants) and Mot-H-K- (H1- or fla- mutants). The transduction transfer of the sign of motility by phage P22HT to H-K- mutants and to H1- and flaE- mutants led to the restoration of agglutination ability with respect to H- and K-antisera in all Mot+ transductants under study simultaneously. The restoration of H+K+ phenotype was also observed in spontaneous motile revertants obtained from H-K- mutants. Thus, the gene controlling the synthesis of K-antigen in Salmonellae was shown to be incorporated into the Fla operon, the regulatory system of the operon controlling the expression of this gene.

[Mapping of the genetic determinant controlling Salmonella K-antigen synthesis. I. Localization of the determinant in conjugation experiments]. / Kartirovanie geneticheskogo determinanta, kontroliruiushchego sintez K-antigena sal'monell. Soobshchenie I. Opredelenie lokalizatsii determinanta v opytakh kon"iugatsii.

The preliminary data on the localization of the gene responsible for the synthesis of K-antigen in salmonellae were obtained. Using Salmonella Hfr donors with different onset of the transfer of chromosomal markers and with phenotype K+, the authors selected different classes of recombinants in the process of their crossing with K- recipients. The positive result of the agglutination test with specific K-antiserum indicated that the transconjugate thus obtained possessed phenotype K+. The gene responsible for the synthesis of K-antigen was shown to be localized between minutes 46 and 41 of the genetic map of S. typhimurium. This gene was not cotransduced with the histidine marker localized on minute 44 of the map.

[Errors in the bacteriologic diagnosis of dysentery and ways of eliminating them]. / Oshibki pri bakteriologicheskoi diagnostike dizenterii i puti ikh ustraneniia.

The study of 1023 strains, formerly identified as Shigella, has revealed that 67 of these strains belong to Escherichia, Enterobacter, Klebsiella, Providencia, Pseudomonas, Flavobacterium. Such errors are due to the insufficient use of biochemical tests in the process of identification. To improve Shigella identification, after the evaluation of changes in Olkenitsky's medium of trisaccharide agar the tests for urease activity, citrate and acetate assimilation, lysine decarboxylase, mobility at 22 degrees C, sensitivity to Shigella bacteriophage, oxidase are recommended.