INCREASE IN BACTERIOPHAGE RADIATION-RESIS TANCE AS A RESULT OF ENHANCED EXPRESSION OF STRESS SYSTEMS IN HOST-CELLS

By means of polyacrylamide gel electrophoresis (PAGE) of proteins from radiation-resistant Gam(r) mutants of Escherichia coli, it was shown that induction and elimination of RecA protein in these mutants are ki netically more rapid than in wild type cells, and heat-shock proteins (HSP) are hyperproduced even at a normal temperature (32 degrees C). g amma- and UV-irradiated bacteriophages were used to study the results of simultaneous enhanced expression of two stress repair systems. Radi ation-resistant mutants are similar to wild type cells in their abilit y to reactivate phages lambda CI, phi 80 vir, and T 4D inactivated by gamma-rays and UV-light. W-reactivation of gamma-irradiated phages lam bda and 80 vir is respectively 1.5 and 1.2 times higher in Gam(r) cell s 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-reactiv ation was registered at doses of 400 to 450 Gy. The phage lambda gamma -, irradiated upon adsorption on the cells of a radiation-resistant mu tant, was two times more resistant to gamma-rays (DMF = 2 at LD(10)) t han when irradiated upon adsorption on wild type cells. Postirradiatio n degradation of the phage lambda DNA, when irradiated within Gam(r) c ells, was significantly lower than in wild type cells, and preirradiat ion of the cells decreased phage DNA degradation (12% in Gam(r) cells and 30% in wild-type cells). The role of an increased HSP level and ex pression of SOS-regulon in radiation resistance and possible interacti on of stress systems in bacterial cells are discussed.