[Features of expression of the genetic region of plasmid pAP42, controlling the synthesis of "sex" pili and surface exclusion system in various E. coli cells]. / Osobennosti ékspressii geneticheskoi oblasti plazmidy pAP42, kontroliruiushchei sintez "polovykh" pilei i sistemu poverkhnostnogo iskliucheniia, v raznykh kletkakh E. coli.

The results of investigation of serologically--typed and nontyped E. coli cells carrying F-like derepressed plasmid pAP42 testified to the influence of genome of some bacterial hosts on the expression of plasmid genetic region determining "sex" (plasmid--specific) pili synthesis and surface exclusion system (Sfx--system). Similar changes in bacterial cells phenotype can also result from the mutational changes of this plasmid.

[Pili determined by the tra genes of F-like plasmids]. / Pili, determiniruemye tra-genami F-podobnykh plazmid.

The study of structural and functional features of plasmid-specific pili synthetized by E. coli cells under control of 27 F-like plasmids was performed. All the plasmids determined the pili of "flexible" type which were classified into 3 groups on the basis of difference in cell sensitivity to pili-specific phages f1, f2, Q. The possible role of transposons in the variation of pili functional properties was supposed.

[Systems of surface exclusion of F-like plasmids of E. coli and their genetic control]. / Sistemy poverkhnostnogo iskliucheniia F-podobnykh plazmid E. coli i ikh geneticheskii kontrol'.

The F-like plasmids belonging to 5 different Sfx-groups were discovered. The existence of atypical plasmids belonging to different Sfx-groups was shown. The molecular cloning of plasmid DNA fragment (3.9 mD) determining SfxII phenotype was performed.

[The transposon content of nonconjugated E. coli plasmids]. / O transpozonovom soderzhanii nekon''iugativnykh plazmid E. coli.

The search of nonconjugated plasmids in antibiotic-resistant cells of wild E. coli strains was performed and their transposon maintenance has been studied. The possibility of existence of some different nonconjugated plasmids in one bacterial cells was shown and each plasmid could carry the same transposon. Insertion of one transposon into the conjugated plasmid pAP42 resulted in numerous deletions in the genome of this plasmid.

[Genetic properties of transposons Tn6-1, Tn6-2 and Tn19-1]. / Geneticheskie svoistva transpozonov Tn6-1, Tn6-2 i Tn19-1.

The level and range transposition of the transposons Tn6-1, Tn6-2, Tn19-1, and their ability to influence plasmid transfer has been studied. The widest range of transposition was shown for transposon Tn6-2. Insertions of each of the studied transposons into different conjugative plasmids genomes resulted in change of frequencies of plasmids transfer and change of plasmids mobilization activity.

[Mobilization for transfer of the nonconjugative plasmid pAP/57Hly by different conjugative plasmids]. / Mobilizatsiia na perenos nekon"iugativnoi plazmidy pAP/57Hly raznymi kon"iugativnymi plazmidami.

The ability for mobilization of E. coli pAP57Hly nonconjugative plasmid which codes for beta-hemolysis production was investigated. It was shown that mobilization of pAP57Hly nonconjugative plasmid does not depend on the incompatibility groups, pili nature, host range of transmissible activity of conjugative plasmids. The data obtained exclude the mechanism of mobilization in which the cointegrative structures are formed.

[Formation of cointegrates during mobilization of nonconjugated plasmids to genetic transfer by plasmid pAP42]. / Formirovanie kointegratov pri mobilizatsii plazmidoi pAP42 nekon"iugativnykh plazmid na geneticheskii perenos.

pAP42 plasmid mobilizes nonconjugative pMR5, pBR322, pACYC 184, RSF2124, RSF1010 plasmids with different frequency. During mobilization of nonconjugative RSF2124 and pACYC184 plasmids by pAP42 factor there form cointegrative structures similar in their properties to typical R plasmids.

[Mobilization capacity of the genetic transfer factors pAP38, pAP-39, pAP41, pAP42 and pAP43]. / Mobilizatsionnaia sposobnost' faktorov geneticheskogo perenosa pAP38, pAP39, pAP41, pAP42 i pAP43.

Study into the mobilization ability of genetic transfer factors pAP38, pAP39, pAP41, pAP42, pAP43 in "three-parent" hybridization has shown that they mobilize unconjugated plasmids for transfer. It is likely that the mobilization mechanism is associated with formation of combined structures by recombination (transfer factor plus unconjugated plasmid).