[Cloning of grisin resistance gene gsr and the study of its functioning in Streptomyces griseus Kr. strain]. / Klonirovanie gena ustoichivosti k grizinu gsr i izuchenie ego funktsionirovaniia v shtamme-produtsente Streptomyces Kr.

S. griseus Kr. is a commercial strain producing grisin, an antibiotic of the streptothricin group used as a feed additive. It was shown earlier that genetic instability of the strain was very high which was evident from a high frequency of nonreverting Grn- Grns mutants. With densitographic analysis of chromosomal DNA electrophoregrams and DNA-DNA hybridization it was revealed that the molecular basis of the genetic instability of the S. griseus strain was deletion of a DNA fragment about 20 kb in size containing a grisin resistance gene. The resistance gene designated as gsr was cloned to S. lividans TK 64 within the plasmid vector pIJ699. The restriction map of a cloned DNA fragment with a gsr gene was constructed and its similarity to that of a nat gene resistant to norseothricin, another streptothricin was observed. Introduction of a gsr gene within the multicopy plasmid pIJ699 into S. griseus 212, a highly productive strain synthesiing the antibiotic, led to an increase in its resistance and productivity. Proceeding from the preliminary data on possible linkage of a gsr gene and grisin biosynthesis genes, it appeared possible to use the cloned gene as a molecular probe in cloning the biosynthesis genes.

[Expression of cloned bialaphos resistance gene (bar) in Streptomyces strains]. / Ekspressiia klonirovannogo gena rezistentnosti k bialafosu (bar) v shtammakh Streptomyces.

The object of the study was a strain of Streptomyces hygroscopicus producing bialaphos, an antibiotic used as a herbicide, which is promising and ecologically safe. Molecular cloning of a bialaphos resistance gene (bar) was performed in the recipient strain, S. lividans TK64, within the 2.0-kb DNA fragment with the plasmid pIJ699. Introduction of a bar gene into another strain producing bialaphos, i.e. S. viridochromogenus Tu494, led to its higher constitutive resistance to bialaphos. The results confirmed the data on different regulation of bar (S. hygroscopicus) and pat (S. virido-chromogenus) resistance genes.

[Recombination in bacteriophage T4: the nature of the disturbances introduced into genetic recombination by a region of non-homology]. / Rekombinatsiia u bakteriofaga T4: o prirode vozmushchenii, vnosimykh v geneticheskuiu rekombinatsiiu oblast'iu negomologii.

Effects of a non-homology region associated with a deletion marker on recombination were studied in two-factor crosses between rII mutants of T4 phage. The basic experimental approach consisted of the comparison of a deletion with the point mutation located at one of the borders of the segment deleted in crosses against the same set of the test markers. The results obtained are in good accordance with the predictions of the model of elastic interaction of migrating cross connection with the nonhomology region. This accordance argues strongly in favour of the hybrid region propagation via branch migration in T4 recombination intermediates.

[Formal genetic study of the enzymology of T4 phage recombination. I. Effect of the antimutational T4 DNA-polymerase on noncorrection-type recombination]. / Formal'no-geneticheskoe izuchenie énzimologii rekombinatsii u faga T4. Soobshchenie I. Vliianie antimutatornoi DNK-polimeraxy T4 na rekombinatsiiu nekorrektsionnogo tipa.

Effect of temperature sensitive antimutator L42 allele of gene 43 of T4 phage on the parameters of non-correction-type mechanism of genetic recombination have been studied under permissive conditions. By comparison of a point mutant with a deletion one, the critical frequency R (xi) corresponds to recombination between two markers separated by a distance equal to mean genetic length of the hybrid region was measured to be 4.15-10(-2). This value exceeds the frequency R (xi) determined with the parallel data in normal (43+) crosses by a factor of 1.6. The length of the hybrid region was shown not to change in the presence of L42 allele. The frequency of formation of the hybrid regions with recombinant flanks and of those with parental flanks increases in the presence of L42 by a factor of 1.3 and 1.8 respectively.

[Morphologico-genetic study of the enzymology of T4 phage recombination. II. Effect of antimutational T4 DNA-polymerase on correction-type recombination]. / Formal'no-geneticheskoe izuchenie énzimologii rekombinatsii u faga T4. Soobshchenie II. Vliianie antimutatornoi DNK-polimerazy T4 na rekombinatsiiu korrektsionnogo tipa.

Effect of temperature antimutator L42 allele of gene 43 of T4 phage on the parameters of correction-type mechanism of genetic recombination have been studied under permissive conditions. The effect of L42 was found to be marker- as well as distance-dependent, and the pattern of these dependences shows that in the presence of antitumor DNA polymerase the distribution of the length of the repair region becomes more sharp and the mean length of the repair region becomes shorter. From this, it is concluded that T4 DNA polymerase is directly involved in the repair of mismatched region in recombinational intermediates, excising non-matched DNA strand and then filling the gap arisen.

[Contritution of correction to genetic recombination in T4 phage measured by the effect of map contraction]. / Vklad korrektsii v geneticheskuiu rekombinatsiiu u faga T4, izmeriaemyi po éffektu suzheniia karty.

Marker-dependence of the fine structure map contraction in T4 phage is studied in two-factor crosses between rIIB mutants separated by indicator distances. The genetic intervals, which were short as compared with mean length of the heteroduplex region in hybrid DNA molecules but which exceeded the length of the DNA strand involved in a single correction event, were selected as indicator ones. On the basis of a deviation of measured frequencies from additivity (map contraction) the marker-specific frequencies of wild type recombinants arising as a result of correction to the wild type (kappa (- leads to +)) were calculated. For the most of the marker studied both of the base substitution and frame shift type the frequencies kappa (- leads to +) have the values below 2.10(-4). In the case of three most highly corrected frame shift markers with kappa (- leads to +) being 14.10(-4)--17.10(-4), about ten percent of all mismatched regions are corrected to the wild type.

[Suppression of DNA-ligase deficiency and selective breeding of mutants and recombinants of T4 phage with phenotype rII]. / Supressiia nedostatochnosti po DNK-ligase i selektivnyi otbor mutantov i rekombinantov s fenotipom rII u faga T4

A number of methods which greatly simplify the introduction of frame shift mutations in the limited segment of the phage T4 rII genes were developed for studying genetical recombination between closely linked markers. These methods enable to construct multiple rII mutants with relatively small expenditure of labour. Suppression of gene 30 deficiency by rII mutations has been studied for a variety of conditions. The results obtained indicate that rIIB polypeptide is involved in two different activities: rIIB region which is dispensable for growth on lambda-lysogenic Escherichia coli strains behaves as indispensable in phenomenon of suppression of ligase deficiency.