Synthesis of ATP and Recovery from Damage by Ultraviolet or γ-Irradiation in Yeast

Abstract

THE viability of irradiated yeast may be enhanced by incubation either in water in aerobic conditions (after exposure to X or ultraviolet radiation) or in 0.5 per cent glucose solution in anaerobic conditions (after X-irradiation) before plating^1,2. Recent work^3–5 suggests that dark reactivation in organisms other than yeast, particularly in ultraviolet irradiated bacteria in nutrient media, is based on the enzymatic repair of potentially lethal structural defects in DNA. The stages of this repair are repair-replication processes which are strongly energy dependent. It is not known whether the same mechanisms operate in yeast incubated in water after ultraviolet or γ-irradiation. If they do, recovery of cells in this condition should be sensitive to inhibition of ATP synthesis. I wish to present data which indicate that recovery from γ-injury is not influenced by treatment of yeast with inhibitors of phosphorylation, whereas dark reactivation in yeast exposed to ultraviolet radiation is much inhibited by this treatment.