Protection and host cell repair of irradiated lambda phage. 3. Ultraviolet irradiation of 5-bromouracil-substituted phage.

Abstract

5-bromouracil-containing λ phage, irradiated with UV light in the presence and absence of cysteamine, were assayed on normal and DNA-repair deficient bacteria. It has been found that these phage suffer (1) lesions, of unknown nature, which are neither reparable by the bacterial DNA repair systems nor prevented by cysteamine, a free radical scavenger and proton donor; (2) lesions which are converted to reparable lesions by cysteamine, and which may be sugar damages (perhaps accompanied by pyridimine dimers) which are converted to simple dimers; and (3) irreparable lesions, which do not occur in the presence of cysteamine, and which are probably sugar damages. These latter are the most important, and in large part explain the increased sensitivity to irradiation of 5-bromouracil-substituted phage. © 1969 Springer-Verlag.