A post-irradiation recovery of the cell I The effect of pre-irradiation cultivation conditions on the repair of radiation damage in Escherichia coli B
Cultivation of E. coli B on minimal medium M-9 at 37oC or nutrient medium at 435[degree] before irradiation resulted in an increase of the survival of X-ray irradiated bacteria as compared with the control. After irradiation, the survival rate was as high as in the case of maximal repair of the control. A similar increase in the survival rate was observed when the bacteria taken in the logarithmic but not in the stationary phase were grown at 43.5[degree] only for the last 1.5-3 hr. (during the previous 10 hr. the cultivation temperature was 37[degree]). The transfer of E. coliB cultivate at 43.5[degree] during the last 1.5-3 hr. to conditions of 37o partially eliminates the effect of growth at conditions of elevated temperatures befor irradiation. Li the case of a-irradiation, the cultivation on M-9 and nutrient medium at 43.5[degree] before irradiation did not increase the survival rate of bacteria as compared with the control (in the latter case, the sensitivity of bacteria to [alpha]-rays was slightly increased). As no repair was observed after [alpha]-irradiation, the increase in the survival number of bacteria after X-irradiation related to changes in cultivation conditions before irradiation may be due to the postirradiation recovery. The results may be explained by the initiation of metabolic mechanisms which determine the activity of the reparation system of the cell.