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V A Lantsov

Publications and source records attributed to V A Lantsov.

8 recordsLinked to original sources
PubMed1977

[Bacterial recombination].

The most perspective trends in studying the mechanisms of genetic exchanges in bacteria are discussed. They are the following. 1. Comparison of the recombination stages in various biological phenomena such as transformation, transduction (generalized), conjugation (common and single-stranded) and transfection. 2. Characterization of genetic determinants and basic enzymes of the recombination process in Rec-systems of different bacteria. 3. Determination of some peculiar features of the intragenic recombination and finding a possible approach to their research. 4. Analysis of some plastic properties of the DNA structure and their application to the modern ideas in the formulation of a molecular mechanism of genetic recombination.

Bacillus subtilis↗
PubMed1977

[Single-stranded conjugation in Escherichia coli K-12: characteristics of the formation of a heterogenous progeny].

During a single-stranded conjugation donor DNA, being a single-stranded form, takes part in the process of recombination. That is why a heteroduplex DNA must be an intermediate product of the recombination. The heteroduplex can be partially corrected as it was supposed for genetic transformation. The division of such a corrected heteroduplex gives the heterogenous progeny of exoconjugants. And this "correctional" heterogeneity must possess two following properties: 1) the mixed progeny must consist of only two recombinational genotypes; 2) the heterogeneity must be marker-specific. The experimental support to both predictions was obtained by the method of clonal analysis of conjugational merozygotes.

Conjugation, Genetic↗
PubMed1977

[Mechanism of genetic recombination in bacterial conjugation. VIII. The heterogeneity of the progeny of exconjugants].

It is shown on several examples that the heterogeneity of recombinant clones after conjugation is independent on the conditions of primary selection (i.e. on the yield of primary clones). Therefore the prediction of the model of autonomously multiplying donor fragments is not confirmed by experimental data. Two additional characteristics of heterogeneity are introduced. The statistical distribution of merozygotes according to segregation time is measured. It is an exponential curve with a relaxation time approximately coinsident with the third cell division. A liner function is found for the dependence of heterogeneity on the distance between the selective and non-selective markers. The highest value for non-linked markers is about 15%. Alternative models for the explanation of the heterogeneity of exconjugants are discussed.

Bacteria↗
PubMed1976

[Mechanism of genetic recombination during bacterial recombination. VI. Single-stranded conjugation].

The mutation BT43 in the dnaB gene inhibits conjugational DNA synthesis in the recipient cell at 42 degrees C. Since only one DNA strand is transferred from the donor to the recipient in these conditions, this single strand is integrated into the recipient chromosone. This is characterized by a high increase of recombination frequency per length unit, an effect well known in the case of transformation. This peculiar genetic process is proposed to be called "single stranded conjugation". It is more efficient in recipient cells recB-recC-sbcB-lacking two main degrading enzymes, exonucleases I and V. The proof of single strandedness was given by means of clonal analysis in a special experiment. The transfer of the selected marker into the thermosensitive recipient took place at 37 degrees C and the transfer of the non-selected marker -- at 42 degrees C. Thhe progeny of one merozygote must be mixed i.e. consist of cells with both alleles of the non-selected marker. This was confirmed by experimental data.

Conjugation, Genetic↗
PubMed1975

[Mechanism of conjugation in Escherichia coli K-12. IV. Conjugation in conditions of phenotypic suppression of gene dnaB mutation].

The thermosensitive mutation BT43 in the gene dnaB is a missence mutation affecting the vegetative and conjugational DNA synthesis. By means of the increase of ionic strength (NaCl concentration) in the medium the functional activity of the dnaB product is partially restored in non-permissive conditions. In these conditions a rescue of recombinant yield is observed. But the mechanism of recombination is switched from one-stranded to double-stranded. This is demonstrated by the alteration of the degree of linkage of genetically close markers.

DNA, Bacterial↗
PubMedDate not supplied

[Evidence for Campbell's mechanism for fine excision of Tn9 type transposons in Escherichia coli K12].

The plasmid-transposon Tn9-322 was constructed by inverted transposition from the pBR322::Tn9 plasmid. The precise excision of the Tn9-322 transposon from the proB gene site can proceed by the Campbell's model. This fact was demonstrated by appearance of the plasmid-transposons after their precise excision. They contain two IS1 elements flanking a short direct repeat of the target DNA. The recombinational mechanism of precise excision of Tn9 type transposons seems not to be alternative but looks as an additional one to a well-known slippage mechanism proved for Tn5 and Tn10.

Base Sequence↗