[Using the laboratory strains of Escherichia coli for studying colicinogenicity].

The indicator system which includes laboratory strains of Escherichia coli K12, K12-C600, BE, and C-Ia is offered for studying colicinogenicity. It has helped to establish that 32 of 100 patients with dysbacterioses of colon carry a colicin-producing strain of E. coli. A tendency is discovered to the increase of occurrence of colicinogenic strains of escherichias with patients' age. Only 24% of E. coli strains form active colicins in a group of one-year old children. Frequency of colicinogenic strains occurrence increases to 33 and 42 %, respectively, in teenagers and adult patients. A strict decrease of total activity of colicins is the main peculiarity of polymicrobe associations in which the prevailing strain of E. coli is accompanied by 3-5 strains of other enterobacteria. As to their sensitivity of colicins the indicator strains are arranged in the following order: K12-C600 (84%), KR (69%), BE (63%) and C-Ia (47%). In spite of that, the low-sensitive strains can be effective for identification of very specific colicins. Since the laboratory strains of E. coli K12, BE and C-Ia are the hosts for specific bacteriophages of E. coli, the indicator system on their basis may be useful for studying the interrelation between colicins and coliphages, as well as plasmids and restriction-modification systems. The paper is presented in Russian.

[Mu-induced deletions and mutations of Erwinia carotovora chromosomes, including resident prophages E105 and 59]. / Mu-indutsirovannye deletsii i mutatsii khromosomy Erwinia carotovora, vkliuchaiushchie rezidentnye profagi E105 i 59.

The plasmid RP4::Mu cts62 in stably inherited by Erwinia carotovora 268 strain. Under the conditions of thermoinduction bacteriophage Mu is segregated and completely eliminated more intensively than in Escherichia coli cells. At thermoinduction the transposition of bacteriophage Mu cts62 into different chromosomal sites takes place, causing the induction of chlorate resistant and auxotrophic mutants with the frequency of 10(-4). Two clones deficient in production of 2 of the 4 resident prophages of Erwinia carotovora 268 strain were found among Mu-induced mutants. The deleted prophages are E105 and 59. DNA-DNA hybridization has revealed the complete and partial deletions of bacteriophage E105 with the level of L-asparaginase production in the cells remaining intact. The damage of the prophage 59 is probably caused by point mutations or short deletions.

[Erwinia carotovora as a recipient system for the natural hybrid plasmid RP4::Mu cts62]. / Erwinia carotovora kak retsipientnaia sistema prirodnoi gibridnoi plazmidy RP4::Mu cts62.

The plasmid RP4::Mu cts62 is transferred from Escherichia coli cells into a recipient strain Erwinia carotovora 268 by conjugation with the frequency 1.5-5 x 10(-7) per donor cell. The maximal frequencies of transfer are obtained by cultivation of donor and recipient cells for 3-5 h on the filters. Structural and functional validity of the plasmid in transconjugants is expressed in preservation of all antibiotic-resistant markers of RP4, thermosensitivity to growth at 42 degrees C as well as spontaneous and thermally-induced production and zygotic induction of bacteriophage determined by the genome of Mu cts62, total length of the plasmid restricts. Location and orientation of Mu cts62 genome in the plasmid restricts. Location and orientation of Mu cts62 genome in the plasmid RP4::Mu cts62 in Erwinia carotovora transconjugant cells has been determined. A single bacteriophage genome has been shown to transpose into the chromosome of the cell with the elimination of RP4 fragment under the conditions of thermal induction.

[The multiple effect of plasmid RP4::Mu cts 62 in transcipient bacilli]. / Monzhestvennyi éffekt plazmidy RP4::Mu cts 62 v transtsipientakh batsill.

Transfer of conjugative hybrid plasmid RP4::Mu cts 62 from Escherichia coli into Bac. cereus, Bac. thuringiensis, Bac. mesentericus and Bac. polymyxa cells led to the multiple effects on the structure and physiology of bacillus cells. It has resulted in a decrease of the bacillus vitality, in the accelerated autolytic decay of cells, in the delay of cell growth and reproduction rate in liquid and solid media, in the disruption of ultrastructure of the cell membrane and its surface layer.

[The infection of bacilli by Mu cts phage integrated into the plasmid]. / Infitsirovanie batsill fagom Mu cts, integrirovannym v plazmidu.

The infection of Bacillus thuringiensis, B. cereus, B. mesentericus and B. polymyxa strains with temperate E. coli bacteriophage Mu cts62 integrated into plasmid RP4 under conditions of conjugative transfer is shown possible. The investigated strains of bacilli are not able to produce intact phage particles but they acquire the thermosensitive property determined by the phage genome. Gel electrophoresis and blot hybridization of DNA have confirmed the transfer of Mu cts62 genome or a part of it in the investigated strains of bacilli.