[Growth of radiation resistance in bacteriophages as a result of intensifying expression of the stress system in host cells].

By means of polyacrylamide gel electrophoresis (PAGE) of proteins from radiation-resistant Gamr mutants of Escherichia coli, it was shown that induction and elimination of RecA protein in these mutants are kinetically more rapid than in wild type cells, and heat-shock proteins (HSP) are hyperproduced even at a normal temperature (32 degrees C). gamma-and UV-irradiated bacteriophages were used to study the results of simultaneous enhanced expression of two stress repair systems. Radiation-resistant mutants are similar to wild type cells in their ability to reactivate phages lambda CI, phi 80 vir, and T 4D inactivated by gamma-rays and UV-light. W-reactivation of gamma-irradiated phages lambda and 80 vir is respectively 1.5 and 1.2 times higher in Gamr cells in which maximal w-reactivation was observed at wide range of doses (from 300 to 2000 Gy) whereas in wild type cells the peak of W-reactivation was registered at doses of 400 to 450 Gy. The phage lambda gamma-, irradiated upon adsorption on the cells of a radiation-resistant mutant, was two times more resistant to gamma-rays (DMF = 2 at LD10) than when irradiated upon adsorption on wild type cells. Postirradiation degradation of the phage lambda DNA, when irradiated within Gamr cells, was significantly lower than in wild type cells, and preirradiation of the cells decreased phage DNA degradation (12% in Gamr cells and 30% in wild-type cells). The role of an increased HSP level and expression of SOS-regulon in radiation resistance and possible interaction of stress systems in bacterial cells are discussed.