Exclusion of polyvalent T7-like phages by prophage elements.

The study presents new insights into the process of interaction of T7-like bacteriophages FE44 and BA14 with lysogenic cells. It was demonstrated that single and double lysogens possess Abiphenotype regardless of genera, species and strain of bacteria that initially had normal phage sensitivity. Efficiency of plating of these phages is reduced by two orders of magnitude on monolysogens, whereas it decreases by 4-6 orders on bilysogens. In the latter case, phage infection leads to formation of more than 60% of aberrant capsids in phage progeny. Abortive phage infection is suggested to be associated with defects in general dynamics of the bacterial chromosome in single and double lysogens of Erwinia "horticola" and Escherichia coli.

Phytopathogenic bacteria phenotype conversion as a result of their lysogenisation by coliphage P1.

A set of lysogenic strains of phytopathogenic bacteria Erwinia "horticola" and Erwinia amylovora associated with woody plants was obtained using bacteriophage P1 Cmc1ts100. The phenotype conversion from Cm(S) to Cm(R) was shown to be connected with introducing of authentic prophage DNA of 94.8 kb as a single-copy plasmid into the cells. Prophage state is unstable: P1 plasmid is spontaneously lost with high frequency by the cells. In lysogenic cells the prophage genes of type III restriction-modification complex EcoP1I are actively expressed. The system formed by E. "horticola" 450 and 60 as well as their lysogenic derivatives and specific bacteriophages provides an opportunity to divide the latter into three groups according to the level of restriction in the course of their interaction with the enzyme EcoP1I. The difference in phage responses to the endonuclease presence in a lysogenized host presumably correlates with the number of enzyme recognition sequences and the adsorption sites availability. After the prophage plasmid DNA curing the characteristic value of phage sensitivity of cells is changed. The lysogenic strains obtained in this work allow for the exploration of EcoP1I restriction-modification gene complex interaction with polyvalent phages able to grow not only on E. coli, but also on such phytopathogens as E. "horticola" and E. amylovora.