Genetic determination and mechanism of realization of the thermoinduced radioresistance

A study was made of the influence of the repair genotype of E. coli cells on the realization of the effect of enhanced radioresistance during γ-irradiation at elevated temperatures (40-45 deg C). The effect of the thermoinduced radioresistance (TIR) was diminished significantly but not abolished completely in mutant cells selectively deficient in excision or recombination repair systems (polAl, recB21C22sbcB15, recF143 mutants). However mutations which exclude the recA gene product (recA13, recA13B21C22 or lexA3 mutants) inhibited TIR completely. The introduction of recA+ gene into recA- or lexA- mutants almost normalized TIR. On the basis of the data obtained the authors discuss the role of recA protein in activation of the membrane-associated repair complex whose effieiency depends on the temperature of γ-irradiation