title: Enhanced response of the Salmonella mutagenicity test to ionizing radiations.
abstract: Gamma-ray-induced reversions in the Ames Salmonella tester strain TA2638 have been studied for their dependence on a number of experimental parameters. It is shown that exposure to ionizing radiations soon after plating is not the procedure that yields results which correspond to those obtained in the standard utilization of the test with chemical mutagens. The ability to detect mutants is improved by irradiation 6 hr after the beginning of the incubation of the plated bacteria. This procedure has the double advantage of a markedly increased ratio of radiation-induced to spontaneous revertants and of resulting in substantial insensitivity to fluctuations in the number of bacteria initially plated. The reversion-doubling dose so obtained is 1.3 Gy; i.e., it is sufficiently small to disregard inactivation of the bacteria.
mesh_terms: D003037:Cobalt Radioisotopes; D004307:Dose-Response Relationship, Radiation; D006639:Histidine / Q000494:pharmacology; D009152:Mutagenicity Tests; D012475:Salmonella / Q000254:growth & development / Q000528:radiation effects*; D013997:Time Factors
chemical_list: D003037:Cobalt Radioisotopes; D006639:Histidine