[The combined action of ionizing radiation and sodium nitrate on bacterial cells].

The survival of bacterial cells Escherichia coli exposed to sodium nitrate (1-5 M) simultaneously with 60Co gamma rays was shown to be smaller than that expected for independent addition of the effects induced by each of agents applied separately. The synergistic effect was quantitatively estimated by the factor k, which is the ratio of the isoeffective doses on the calculated additive survival curve and the experimental one. The dependencies of k on the exposition of combined action of gamma rays and different NaNO3 solutions (1, 3 and 5 M) are presented. It was demonstrated that the synergistic ratio k was increased with exposure duration increasing. It is suggested that in this case the synergistic effect may be related with the formation of some additional lethal damage due to NaNO3 radiochemical transformation products.