Factors in the Inactivation of T2 Bacteriophage and Mono-complex by Ionizing Radiations

Abstract

SummaryThe rate of inactivation of T2 phage and the T2 E. coli B mono-complex by 50 kv x-rays or by γ-rays was investigated. The phage were protected from indirect radiation action by nutrient broth or thiourea, and the irradiations were carried out in the presence or in the absence of oxygen. It was found that oxygen had very little effect on the inactivation of the phage, but that the presence of oxygen doubled the rate of inactivation of the complex. This change in the oxygen effect appears to occur as soon as the phage-DNA enters the bacterial cytoplasm and is independent of whether cyanide is added before adsorption. The results are discussed in terms of the reactions of a radiation-induced carbon radical in the phage-DNA which may (1) combine with molecular oxygen and become inactivated, (2) react with a cytoplasmic hydrogen-atom donor and regain the active configuration or (3) become inactivated by a third unknown process if neither oxygen nor a hydrogen donor is present.