A New After-effect of X-Rays on Dilute Aqueous Suspensions of Bacteriophage

Abstract

IF dilute aqueous suspensions of bacterial virus are exposed to X- or γ-rays, inactivation of the virus continues after the cessation of radiation. After doses of about 15,000 r. to the dysentery phage S13, or about 2,000 r. to the coliphage T3, the number of phage particles forming plaques is reduced in an hour to less than 10 per cent of the number still surviving at the end of the irradiation. It has been briefly reported¹ that the rate of inactivation after the end of radiation is greater than that found as a result of adding to phage suspensions the amount of hydrogen peroxide which would be produced by the radiation. It has now been established that the greater part of the delayed inactivation of phage after the end of irradiation is due to a change in the phage, occurring during irradiation, which makes it much more susceptible thereafter to the action of added hydrogen peroxide or of the hydrogen peroxide formed by the radiation in the suspending medium.