Interaction of X-ray and Ultraviolet Ray in Killing Cells

Abstract

THE importance of DNA as a macromolecular target for cellular inactivation by X-rays and ultraviolet light has been stressed by various authors¹. The two mechanisms of inactivation, however, have been suggested to be different^2,3. Studies of the killing of various bacteria by X-rays and ultraviolet light have suggested that preliminary exposures to ultraviolet increase the sensitivity of the cells to X-rays but preliminary exposure to X-rays can only remove the shoulder of the ultraviolet-survival curve⁴. We have repeated these interaction studies with strains of E. coli B, B/r and B_s–1 and substantially corroborated the finding. But in the case of an auxotrophic strain, E. coli 15 T–A–U– requiring thymine, arginine and uracil, the findings were rather different. We report here the results of one such experiment.