The bactericidal action of X-rays, neutrons and radioactive radiations

Abstract

Experiments are reported in which the bactericidal effect of α-, β- and γ-rays of radium, X-rays of various wave-lengths, and neutrons, has been observed, particularly on Bact. coli and spores of B. mesentericus. It is shown that the survival curves are exponential and that the lethal dose is independent of the intensity of the radiation and of the temperature during the irradiation. The lethal dose varies for different radiations, being, in the case of vegetative bacteria, greatest for those radiations, particularly α-rays, which produce their ionizations close together.These experimental facts can all be explained on the view that the “lethal” action of radiation is really the production of lethal mutations. It is deduced that the number of “genes” in Bact. coli is of the order of 1000.