[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].

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.

[The molecular cloning of a genetic region determining the surface exclusion system of the F-like plasmid pAP42].

Molecular cloning of genetic region of F-like plasmid pAP42, coding its surface exclusion system (system Six V) was performed. Restriction and genetic analysis of recombinant plasmids showed that six V locus is situated in Sal I-fragment f5 (4.2 MD) of this plasmid.

[Genetic region of incompatibility of the F-like plasmid pAP-18-1].

With help of molecular cloning the genetic region controlling incompatibility of plasmid pAP18-1 (Inc FXI) was localized in EcoR1-fragment f5 (3.6 MD). The genetic region of incompatibility of its derepressed mutant pAP18-1drd (Inc FVII) is situated in EcoR1-fragment f2 (7,2 MD).

[Pili determined by the tra genes of F-like plasmids].

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.

[Systems of surface exclusion of F-like plasmids of E. coli and their genetic control].

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.

[Genetic organization of transfer region of F-like plasmid pAP18-1].

The results of complementation analysis of nitrosoguanidine-induced mutants of F-like drd-plasmid pAP18-1 (Tc, ColV) testified to the existence of at least 3 tra regions (tra1, tra2, tra3) and regulating locus fin V in the genome of this plasmid. By means of molecular cloning of tra2 region and locus fin V of plasmid pAP18-1drd were located in Sall-fragment f5 (3.9 MD).

[Cloning of DNA fragments of the genetic transfer factor pAP39].

Large HindIII digested fragments of the plasmid pAP39 have been cloned on the cosmid vector pHC79. The study of the structure of HindIII fragments of plasmid pAP39 in the recombinant plasmids has shown that these fragments are represented by f1 + f2 fragments from the plasmid pAP1055, by f1 + f6 fragments from the plasmid pAP1056, by f2 + f3 fragments from the plasmid pAP1057 and by two f3 fragment from the plasmid pAP1058. Physical maps of the recombinant plasmids have been constructed.

[Restriction mapping of genetic transfer factor pAP39].

A model of calculation of molecular weights of fragments EcoRI, Hind III and PvuI is formulated. A restriction site map of factor pAP39 is constructed automatically. Sites to EcoRI and PvuI are distributed in the segment with molecular weight 9.