Temperature Dependence and Effect of Glycerol on the Radiation Sensitivity of Bacteriophage-Escherichia coli Complexes Related to Direct and Indirect Radiation Effect

Abstract

A test system of T2r bacteriophage DNA injected into the Escherichia coli host (1- or 2-minute development at 37°C) permitted experimentation with biologically active DNA in a cellular environment. By irradiation of this system in the liquid and frozen state with cobalt-60 γ-rays at various temperatures, an estimate of the contribution of direct and indirect radiation effect was made. It was concluded that: 1. Not more than 33% and perhaps as low as 15 to 20% of the radiation effect on T2r DNA in a host bacterium is by direct radiation effect; the remainder is by indirect effect. Percentages of the same magnitude were found for irradiations in air and in nitrogen. An oxygen effect of 1.6 was found in the liquid state and the frozen state. 2. The addition of 1 M glycerol (in air) confers radiation protection in the liquid and the frozen state. The protection is threefold at 0°C and about 35% at -160°C. 3. The activation energy derived for frozen phage-bacterial complex in 1 M glycerol is similar to that fo...