[Pathogenicity of Francisella].

The data of literature and the results of the author's research on the pathogenicity of the causative agent of tularemia and other Francisella organisms are reviewed. The solution of the problem of their pathogenicity is based, as stated by the author, on the level of our knowledge of the genetics of Francisella. The conclusion has been made that scientific achievements in the field of the genetics of Francisella, obtained during the last 15 years, make it possible to find out the pathogenicity factors of the causative agent of tularemia, as well as other microbes of the family Francisella.

[The role of surface structures of recipient cells in bacterial conjugation]. / Rol' poverkhnostnykh struktur kletok-retsipientov pri kon''iugatsii bakterii.

Previously, while studying conjugation process in bacteria, the main attention was given to donors of plasmids. The aim of this review is to show that recipient cells indeed play an important role in this process too. The main attention is given to the structure of recipient cell walls, which is necessary for the recognition of donor cell pili and the establishment of the contact between the cells, i. e. to the first steps of conjugation between gram-negative microorganisms. The evidence concerning the influence of recipient cell walls defects on transmission of some plasmids is presented. The significant role of defects in lipopolysaccharide structure and of the intrinsic features of protein components of the outer membrane is considered. To the author's mind, the diversity in the cell wall structure creates the "outer barriers" for the plasmid exchange between different bacteria. Like the "inner barriers" (restriction, transcription, mistakes, plasmid incompatibility, etc) these "outer barriers" seem to be crucial for genetic isolation of bacterial species. Postulating this process, the author puts forward the idea of applicability of the conception of the biological species to prokaryotes.

[What are toxins to microbes? (the role of toxins in bacterial ecology)]. / Zachem mikrobam toskiny? (o roli toksinov v ékologii bakterii).

The author attempts to answer two questions: whether the toxins, in particular the toxins having their specificity connected with enzymatic activity, are needed for microbial cell physiology and their significance for bacteria that are not the obligate parasites for warm blooded animals. The analysis of literary data supposes the toxins to be essential cellular metabolites since many of them participate in energy acquiring. Besides that a number of toxins is shown to be relevant to microbial life and to affect the micropredators, especially the monocellular organisms feeding the microbes. In connection with the above mentioned, special attention is paid to extrachromosomal location of many toxins genes relating them to bacteriocins. The possibility is not excluded that in the future the new toxins might come to be found having the enzymatic activities.

[The "side-effects" of plasmids (R-plasmids and virulence)]. / O "pobochnykh" éffektakh plazmid (R-plazmidy i virulentnost').

Many plasmids affect the host cells. Their effects cannot be explained only by the expression of the well-known genes coding for antibioticresistance, bacteriocinogeny and hemolysis or the analogous genes (side-effects). The side effects are not characteristic of all plasmids operating under similar conditions. Forecasting of the side-effects inducikility by any definite plasmid is impossible now. Sometimes the same functions exert the contrary effects on the bacterial cell. The connection between the presence of plasmids, especially R-plasmids and the complex cellular property, virulence, is of great interest. Often, bacteria become less virulent obtaining the plasmids. Two possible reasons causing such an effect are discussed. The first one is a direct effect of plasmids on cellular physiology. The second reason is connected with population shifts caused by the fact that the cells with initial low virulence possess the recipient ability predominantly. The decreased virulence of bacteria harbouring R-plasmids, in authors opinion, is quite a natural phenomenon based on plasmid host cells adaptation to the existence in "the realm of antimicrobial agents".

[Transposon-mediated integration of the RP1 plasmid into chromosomes of methylotrophic bacteria]. / Transpozonoposredovannaia integratsiia plazmidy RP1 v khromosomu metilotrofnoi bakterii.

The homology region between the DNA of plasmid RP1ts::Tn601 and chromosome of the thermotolerant methylotrophic bacterium Methylobacterium sp. SKF240 has been constructed by transposon Tn601 translocation into the chromosome. The clones of Methylobacterium sp. SKF240 having integrated the plasmid RP1 into the chromosome have been obtained by conjugation on the basis of above mentioned genetic technique. The integration of plasmid RP1 into the chromosomal DNA of the methylotroph has been confirmed by the genetic and electrophoretic methods. Clones harbouring the integrated plasmid are able to transfer the chromosomal genes for methionine and isoleucine-valine synthesis to the recipient cells of P. aeruginosa PAO ML4262 by conjugation.

[Transfer of prophage Mu into methylotrophic bacteria in the plasmid RP4]. / Peredacha profaga Mu metilotrofnym bakteriiam v sostave plazmidy RP4.

Bacteriophage Mu genome has been transferred into the cells of Pseudomonas methanolica and Methylobacterium sp. SKF240, that are naturally resistant to the bacteriophage, as a fragment of a hybrid plasmid RP4::Mu cts62. Temperature induction of the bacteriophage results in host cell lysis. Plasmid RP::Mu cis62 is maintained in methylotrophic cells presenting a cointegrative structure. The genetic and electrophoretic, analyses of the DNA isolated from transconjugant cells have confirmed the conclusion. Bacteriophage Mu propagation has been shown to be restricted in methylotrophic cells.

[Features of the interaction of Escherichia coli and Francisella tularensis RNA polymerases with hybrid plasmids bearing fragments of Francisella tularensis chromosomal DNA]. / Osobennosti vzaimodeistviia RNK-polimeraz Escherichia coli i Francisella tularensis s gibridnymi plazmidami, nesushchimi fragmenty khromosomnoi DNK Francisella tularensis.

Hybrid plasmids containing the fragments of Francisella tularensis chromosomal DNA and capable of tet-gene expression both in Escherichia coli and Francisella tularensis cells were constructed. The regions of francisella chromosomal DNA binding the RNA-polymerases of Escherichia coli and Francisella tularensis were found by the electron microscopy technique. Interconnection of those regions with the expression of tet-gene of the hybrid plasmids was demonstrated.

[Behavior of Sa plasmid in tularemia pathogen cells]. / Povedenie plazmidy Sa v kletkakh tuliaremiinogo mikroba.

The genome of Sa plasmid is shown to be a subject of genetical rearrangements in Francisella tularensis cells. The rearrangements either result in plasmid integration into the host cell genome or intramolecular amplification of cat-gene with the subsequent excision and recombination of the derivative plasmids. Stable inheritance of the plasmid is registered after integration while plasmid elimination occurs in case of extrachromosomal localisation.

[Study of CAT gene expression in Sa and pC194 plasmids in Escherichia coli, Francisella tularensis, and Bacillus subtilis cells]. / Issledovanie ékspressii CAT-genov plazmid Sa i pC194 v kletkakh Escherichia coli, Francisella tularensis i Bacillus subtilis.

The unit activities were defined for chloramphenicol-acetyltransferases coded for by the cat-genes of the plasmids Sa and pC194 in Francisella tularensis, Escherichia coli and Bacillus subtilis cells. Francisella tularensis cells were shown to hold intermediate position between Escherichia coli and Bacillus subtilis cells in their ability to express the genes of the different taxonomic origin. The direct dependence was found between the dose of the gene coding for chloramphenicol-acetyltransferase synthesis and efficiency of the gene expression, minimal inhibiting concentration of the antibiotic and colony size on the media containing chloramphenicol.

[Transfer of bacteriophage PRD1 genes into modified plasmid Sa of Escherichia coli and Francisella tularensis cells]. / Perenos genov bakteriofagov PRD1 v modifitsirovannye plazmidoi Sa kletki Escherichia coli i Francisella tularensis.

The donor specific bacteriophage PRDI has been shown to mediate the genes transfer into Escherichia coli and Francisella tularensis cell under certain conditions. It is necessary for the process that the recipient cells inherit the plasmids determining absorbtion of bacteriophages on the cellular surface while the transferred genes are able to be expressed. The frequencies of the tet-gene transfer from the plasmid pSKFT5 into Escherichia coli and Francisella tularensis 15 cells inheriting the plasmid Sa are, correspondingly, 10(-6) and 10(-7) clones per bacteriophage plaque.

[Biochemical bases for the effect of combining kanamycin and nitrofuran resistance genes in Escherichia coli cells]. / Biokhimicheskie osnovy éffekta sovmeshcheniia genov ustoichivosti k kanamitsinu i nitrofuranam v kletkakh Escherichia coli.

The fact of a significant increase in resistance to aminoglycosides when nfr genes with chromosomal or plasmid localization are combined with the plasmid genes coding for kanamycin-transferase in E. coli cells is confirmed. Gel-filtration of homogenates of the cells with and without pLD105 plasmid carrying nfr gene and of the cells with a chromosomal nfr gene revealed a 10 kD polypeptide when the plasmid is present. Relying on these results, it is concluded that the discovered polypeptide fulfils two roles: inhibiting of specific nitrofuran-reductase, which leads to nitrofurans resistance and a drop of transmembrane electric potential contributing to the increase of resistance to aminoglycosides (kanamycin) in strains with the plasmid nfr gene. Absence of the 10 kD polypeptide in the cells with a chromosomal nfr gene and other data are indicative of a possible existence of a different mechanism of resistance to nitrofurans and an increase of resistance to aminoglycosides in the strains with a chromosomal nfr mutation.

[Comparison of the structural-functional properties of DNA-dependent RNA polymerase of the tularemia microbe and intestinal bacterial]. / Sravnenie strukturno-funktsional'nykh svoistv DNK-zaviskmykh RNA- polymeraz tuliaremiinogo mikroba i kishechnoi palochki.

The subunit compositions of RNA-polymerases from Escherichia coli and Francisella tularensis were compared. The activities of the enzymes on the corresponding chromosomal DNAs and their mixtures were defined.

[A new R-plasmid from Yersinia pseudotuberculosis]. / Novaia R-plazmida Yersinia pseudotuberculosis]

Yersinia pseudotuberculosis strain 140-P isolated from soil in the Far East was found to harbour an R-plasmid different from the plasmids that had been isolated from the bacteria previously. A new R-plasmid pLD140 is conjugation proficient and codes for the cellular resistance to streptomycin, tetracycline and sulfonamides. The plasid belongs to incompatibility group IncP. Its restriction endonucleases BamHI and SalI profile is different from the ones of the plasmids belonging to the RP4 family.

[Detailed mapping of the Hly-region of the plasmid pHly241. Homology of the hemolysis determinants of plasmids pHly241 and pHly195]. / Detal'noe kartirovanie Hly-oblasti plazmidy pHly241. Gomologiia determinantov gemoliza plazmid pHly241 i pHly195.

Data on the hemolysin synthesis determined by the plasmid pHly241, belonging to the incompatibility group I2, and its derivatives are presented in this paper. The restriction analysis of the pHly241 plasmid has resulted in the detailed mapping of the hly determinant region in the plasmid. The substantial homology has been demonstrated between the regions of the plasmids pHly241 and pHly195 coding for hemolysin synthesis and excretion from the bacterial cell.

[An current question in the molecular genetics of bacteria]. / Ob odnom aktual'nom voprose molekuliarnoi genetiki bakterii

The author considers the possibilities and limits of extrapolation of the data by the genetics of one species of bacteria to the other. It is emphasized that even in the related bacterial species a similar localization on chromosomes was inherent only to some of the unitypical genes, by in this case as well not all the genes were grouped in the same way, and differed by their delicate structure. An idea on the significant role of genetic metabolism in the microbial evolution is being developed; particular significance is attributed to plasmides. It is supposed that foreign plasmides, particularly transmissive factors of multiple drug resistance could aid in charting the chromosomes of bacteria in which the routes of transmission of genetic information are still unknown. A conclusion was drawn on the necessity of intensification and widening the investigations on the molecular genetics of bacteria of significance for public health and public economy.

[Molecular biological mechanisms of the variability of Helicobacter pylori]. / Molekuliarno-biologicheskie osnovy izmenchivosti Helicobacter pylori.

Nowadays notions on the variability of Helicobacter pylori are reviewed. Genetic polymorphism of H. pylori is manifested by variability of gene properties and their order in different strains due to recombinations occurring in these bacteria much more frequently than in other bacterial species. H. pylori belongs to those bacteria which are capable of natural transformation. Transformation is very often observed both in vitro and in vivo. A significant role in the variability of H. pylori is played by transposons and specific nature of mutagenesis. The author emphasizes that differentiation between the roles played by recombinations and mutations in the variability of H. pylori is difficult. Special attention is paid to the resistance of H. pylori strains to chemotherapeutic drugs and to the mechanisms of its development.

[Helicobacter pylori and its role in pathology]. / Helicobacter pylori i ego rol' v patologii.

The review deals with modern data on the main cultural and biochemical properties, pathogenicity factors and their possible role in pathogenesis. Information on the methods of the diagnostics of diseases associated with H. pylori is given. The routes of the transmission of this infective agent are discussed. The results of experimental data on the genetics and immunochemistry of H. pylori are presented.

[Resistance to levomycetin and activity of several enzymes in Escherichia coli and the agent of plague]. / Rezistentnost' k levomitsetinu i aktivnost' nekotorykh fementov u vozbuditaelia chumy i kishechnoi palochki

The authors compared the activity of acetyl-CoA-synthetase and of the enzymes belonging to the group of asparaginic acid in levomycetin sensitive and resistant strains of Y. pestis and E. coli. There were revealed marked differences in the activity of aspartase, fumarase, synthetase and desamidase of L-asparagin, and also of the enzyme activated by acetate in the E. coli strains with plasmide resistance. Transmission of R-factor to the pestis was accompanied by decomposition of L-asparadein, formation of AC-CoA. At the same time transformation of L-asparaginic acid catalyzed by aspartase remained on the same low level in the sensitive pestis cultures and their variants with the R-factor. When the resistance was controlled by chromosomal resistance markers, the activity of the enzymes providing formation of L-asparagic acid, its amide and L-malic acid showed no significant change. In chromosomal type of resistance in the mutants of pestis and E. coli the acetyl-CoA-synthetase reaction was as a rule somewhat increased.

[New indications for the participation of group P plasmids R in the transfer of chromosomal genes in intergenera crosses]. / Novye ukazaniia na uchastie plazmid R gruppy P v perenose khromosomnykh genov pri mezhrodovykh skreshchivaniiakh.

Use of E. coli strains with phenotypes Rec+ and Rec- asrecipients in intergenera crosses confirmed the supposition put forward by the authors formerly that new chromosomal markers in transconjugantes originated due to Psuedomonas aeruginosa. These chromosomal markers were transferred together with plasmid R conditioning the conjugation, and maintained without being built-into E. coli chromosome. Between the arg+ marker and the plasmid R18 there existed labile physical connection demonstrable only under definite conditions of recombinant selection.

[Temperature-sensitive mutant of bacteriophage D3 and its use for the purpose of demonstrating the location of prophage in Pseudomonas aeruginosa cells]. / Temperaturochuvstvitel'nyi mutant bakteriofaga D3 i ispol'zovanie ego s tsel'iu vyiasneniia lokalizatsii profaga v kletkakh Pseudomonas aeruginosa.

For the first time a thermoinducible mutant, known as D3ct, has been obtained from Pseudomonas aeruginosa phage and used for lysogenizing culture PAO2604 Met--Ilv--. After a temperature shock phage D3ctwas induced from lysogenic strain PAO2604 (D3ct), and its development went along the lytic line. From the population of PAO2604 (D3ct) cells only 0.07% survived; in these cells the faulty excision of the prophage probably occurred at a high temperature. After thermoinduction 2.8% of the colonies formed by the survivors were auxotrophic in leucine. Such frequency of the appearance of the additional nutritional requirement for leucine suggests that the prophage was incorporated into the chromosome adjacent to some gene responsible for biosynthesis of leucine. In the process of faulty excision phage D3 retained a part of the host chromosome.