[Role of phage LØ7 lysogeny in genetic variability of Escherichia coli].

AIM: Determine the possibility of Iysogenization of Escherichia coli single strain DNA (ssDNA) by 1ø7 bacteriophage from the Microviridae family and determine the role of phage lø7 lysogeny in genetic variability of these bacteria. MATERIALS AND METHODS: A method of E. coli K12 lysogenization by phage lø7 was developed. A spot-test for the control of resistance of the obtained lysogens against phage lø7 and determination of lysogen lø7 spontaneous production was worked out. Criteria for phage lø7 identification, that is spontaneously produced by E. coli K12 lysogens, were proposed. A kit of isogenic E. coli strains, that vary by mutations in ptsI, ptsH and fruA genes, that code phosphoenolpyruvate (PEP): carbohydrate phosphotransferase system (PTS) proteins, was constructed. RESULTS: The ability of highly virulent bacteriophage lø7 to lysogenize E. coli was shown. A reduction of lø7 titers in ptsI, ptsH and fruA E. coli K12 mutants was demonstrated compared with titers in wild-type bacteria. Lytic bacteriophage lø7 was also able to lysogenize ptsI, ptsH and fruA mutants at a high frequency. Lysogens are resistant to phages lø7, phiX174 of Microvirus genus and spontaneously produce lø7. CONCLUSION: Bacteriophage lø7 of the Microviridae family is able to lysogenize E. coli K12 and vertically transfer genome of this lytic phage. As a result, lytic phage lø7 takes part in bacterial variability as a factor of lysogen selection in bacteria population corresponding to PTS mutants by phenotype.

[The genetic transfer, heredity and phenotypic expression of plasmid RP4::Mu cts genes in Bacillus cereus]. / Geneticheskii perenos, nasledovanie i fenotipicheskoe vyrazhenie genov plazmidy RP4::Mu cts v 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). The transcipient clone Bac. cereus 682 was selected having stably inherited and expressed the hybrid plasmid PR4::Mu cts 62 genes for antibiotic resistance and temperature sensitivity. Production of the bacteriophage Mu cts 62 particles was not registered in the bacillary transcipient cells. The plasmid RP4::Mu cts 62 genes were localized in the chromosome of Bac. cereus 682 transcipient by the blot-hybridization technique with 32P-labelled DNA of the bacteriophage Mu cts 62 and the plasmid PR4. The transcipient of Bac. cereus 682 has the donor properties and transfers the RP4::Mu cts 62 genes to recipient cells of Bac. cereus DSM 318 with the frequency of 10(-6)-10(-7). The expression and transfer of the gram-negative plasmid genes in gram-positive bacterial cells are discussed.

[Change in the ultrastructure of the cell wall of Bacillus cereus, determined by RP4 MUCTS62 plasmid]. / Izmenenie ul'trastruktury kletochnoi stenki Bacillus cereus, determiniruemoe plazmidoi RP4 MUCTS62.

The influence of plasmid RP4 Mucts62, heterologous for B. cereus, on the growth rate of B. cereus strains GA 682 and 319 obtained in our earlier experiments and on changes in the ultrastructure of their cell walls in comparison with B. cereus initial strains GP 7 and DSM 318 has been studied. Plasmid RP4 Mucts62 with a wide spectrum of action has been found not only to determine the functional signs of resistance to antibiotics and thermal sensitivity in the heterologous host, but also to take part in the morphological organization of the cell surface structure, and in particular in the structure of the S-layer. B. cereus strains containing plasmid RP4 Mucts62 are characterized by slower growth rate and cell fragility.

[Effect of the molecular weight of DNA on the effectiveness of plasmid transformation of E. coli K12]. / Vliianie molekuliarnoi massy DNK na éffektivnost' plazmidnoi transformatsii E. coli K12.

The level of plasmid transformation and transfection by the high molecular mass DNA was studied for Escherichia coli mutants having increased efficiency of plasmid transformation by low molecular mass DNA. Decreased level of plasmid transformation and transfection registered in some mutants as compared to the one in wild type strain suggests the specificity of Escherichia coli cells penetration for DNA of different molecular mass.

[In vivo restriction of Escherichia coli-transforming DNA by endonuclease R.M.EcoRI]. / Restriktsiia transformiruiushchei DNK Escherichia coli éndonukleazoi R.M.EcoRI in vivo.

Transformation of Escherichia coli K-12 for various chromosomal markers was accomplished by using AB1157 recBC+ strain as a recipient. The yield of transformants was reduced 10-fold, as compared with that obtained in JC7623 recBC sbcB recipient. Elimination of transformation has been obtained for arg, pro, his markers in AB1157 (pSA14) harbouring the R.M.EcoRI coding plasmid. Production of restriction endonuclease in this strain did not affect the efficiency of transformation for thr, leu markers. The presence of pSA25 which is isogenic to pSA14 but devoid of R.M.EcoRI genes has been irrelevant to transformation for leu, arg, pro, his, thr markers. Correlation between the restriction of transformed markers in vivo and in vitro is discussed.

[Competence in Escherichia coli cells. V. Interaction of the competence factor with the cells]. / Kompetentnost' u kletok Escherichia coli. Soobshchenie V. Vzaimodeistvie faktora kompetentnosti s kletkami.

Some trends of the interaction of the competence factor with the cells are described on the model of phage lambda transfection. It is shown that this process depends on the composition of the recipients growth media, the temperature regime in the interaction processand on the concentration of the competence factor and the recipient cells. The preliminary treatment of the recipient by EDTA (0.0001 M), CaCl2 (less than 0.02 M), MgCl2 (less than 0.01 M), and NaCl (less than 0.01 M) resulted in the increaze of their sensitivity to subsequent treatment by the factor. Data are obtained demonstrating that after the treatment of cells by the competence factor their sensitivity to decreased CaCl2 concentration is increasing.

[Competency of Escherichia coli cells. IV. Effect of freezing--thawing on the formation of competency in Escherichia coli cells in the presence of Ca++ ions]. / Kompetentnost' u kletok Escherichia coli. Soobshchenie IV. Vliianie zamorazhivaniia--ottaivaniia na formirovanie kompetentnosti u kletok Escherichia coli v prisutstvii ionov Ca++

The paper is initiated in the aim to use the effect of freezing-thawing in the system of intact Escherichia coli cells treated with Ca++ ions to increase the transfection efficiency. It is demonstrated that freezing-thawing of Ca++ treated cells increases the transfection indices of lambda phage DNA for E. coli Hfr clone with low transfection indices in 20-30 times, and for the strain of E. coli X7026 of high competence-in 5 times. Freezing-thawing efficiently increased the transfection only in cells with a decreasing competence. E. coli Hfr H cells acquired the capacity of more efficient lambda phage DNA perception independently on the growth phase, while in E. coli X7026 cells the maximal transfection increase under the effect of complementary interactions was observed at the beginning of the logariphmic and stationary growth stages, but not during the competence period. Short-term changes emerging in cells during freezing-thawing can probably promote the better penetration of Ca++ ions to active sites on the cell surface, which produces favourable conditions for lambda phage DNA formation.

[Competence in Escherichia coli cells. III. Formation of competent states in Escherichia coli X7026 and Escherichia coli Hfr H cells during storage in different conditions]. / Kompetentnost' u kletok Escherichia coli. Soobshchenie III. Formirovanie kompetentnogo sostoianiia u kletok Escherichia coli X7026 i Escherichia coli Hfr H pri khranenii v razlichnykh usloviiakh

The competence formation in 2 strains of Escherichia coli X7026 and Hfr H to isolated phage gamma DNA after the prolonged treatment of cells with Ca++ ions at low temperatures was investigated. In both strains studied the sensitivity of cells to phage lambda DNA increased during several days of maintenance at 4 degrees C in 0.2 M CaCl2, and reached the maximal value in 24-48 hours for E. coli Hfr H cells, and in 72-96 hours for E. coli X7026 cells. Cells maintained in CaCl2 for 24 hours and more interacted more effectively with DNA in the cold, and didn't need Ca++ ions at the last stage of transfection (incubation of the infectious mixture at 37 degrees C) as the freshly grown cells did. Variations induced in the cells after the prolonged action Ca++ ions were preserved only in the presence of CaCl2. After the washing of CaCl2 from the cells with 0.15 M NaCl they returned to the initial state. The competence formation in cells of E. coli X7026 under the effect of Ca++ ions was going on more actively when the cells were preliminary incubated for several days at 4 degrees C in the absence of CaCl2. E. coli Hfr H cells were resistant to this treatment.