Alkali Halides as Agents Enhancing the Lethal Effect of Ionizing Radiations on Microorganisms

Abstract

Actions of alkali halides such as fluoride, chloride, bromide, and iodide were found to enhance the lethal effect of ionizing radiations on cells of bacteria and yeast suspended in 0.067 M phosphate buffer. The data obtained are concerned mainly with the effects of halides present during irradiation. The effects of halide concentration, dose, pH, and freezing on the enhancing actions of halides and also on the aftereffects of irradiation were determined. It was concluded that the possible mechanism for the enhancement by halides may involve the inactivation of a multihit type of short-lived species, which is produced from halide ions by ionizing radiations, but not by ultraviolet light. Different halides, however, appeared to behave differently toward irradiation with respect to forming the long-lived species which could have an influence on the enhancement of radiolethality.