[UV-induction of the LT-toxin operon depending on genes lexA, recA, and umuD].

UV induction of the elt operon (the LT-toxin operon in Escherichia coli) was demonstrated in experiments using fusion of elt::lac operons with the help of Mud1(Ap lac) phage. UV induction of the elt operon is lexA-dependent; thus, the possibility of SOS regulation of this process may be assumed. However, UV induction of the elt operon turned out to be recA-independent, which makes it impossible to consider this induction as a typical SOS response.

[A highly sensitive non-isotopic system of DNA hybridization using amplification (PCR) for identifying and indicating presence of Brucella].

A non-isotopic amplification system was used to identify and indicate Brucella. The terminal sequences of a protein gene fragment in Brucella outer membrane were identified and direct and reverse primers were chosen for a polymerase chain reaction. (PCR).

[The genetic transfer, heredity and phenotypic expression of plasmid RP4::Mu cts genes in Bacillus cereus].

The transcipients were obtained in intrageneric matings of E.coli donor harbouring the plasmid PR4::Mu cts 62 with Bac. cereus GP7 recipient cells with the frequency 10(-9).

[Outer membranes of Francisella tularensis and their protein composition].

Four strains of the species Francisella tularensis were used in the present work: a live vaccine strain 15/10 and three virulent strains (503, Schu, 543) from three different subspecies. The bacterial membranes were prepared by the 0.5% N-laurylsarcosinate (Sarcosyl) treatment.

[UV-inducibility of the LT-toxin operon].

The plasmid elt-operon pVZ14 was constructed by fusing of the eltoperon of the plasmid pVZ357 with the lac-gene of the bacteriophage Mud1 (Amp, Lac). lacZ gene has been proven to be fused with an elt-promoter by the loss of toxin production coded by pVZ357 and acquiring of Lac+ phenotype by pVZ14 containing cells, as well as by HindIII fragments hybridization of pVZ357 and pVZ14 with the labelled elt-probe. The kinetics of beta-galactosidase synthesis in E.

[Use of the DNA-DNA hybridization method on filters for determining the toxic potency of atypical strains of Vibrio cholerae isolated from natural sources].

The methods of the radioimmunoassay and the blot hybridization of restricted fragments of chromosomal DNA have been used for the characterization of V. cholerae atypical strains isolated from the natural environment. For all strains under study, the radioimmunoassay has been found to yield the most sharply defined data characterizing their atoxigenicity.

[Reparation of the damages induced by UV light in salmonellae].

The survival of Salmonella typhimurium wild type strains after UV-irradiation is studied. It is demonstrated that many of these are more sensitive to UV-irradiation than Escherichia coli of the wild type. Alkaline sucrose density gradient centrifugation has demonstrated a deficiency of these strains in normal excision repair of UV-damaged DNA.