Effect of Some Metabolites and Antimetabolites on the Breakdown of Deoxyribonucleic Acid and on the Colony-Forming Ability of Escherichia coli B after Gamma Irradiation: IV. Synthesis of Nucleic Acids and Protein after Removal of the Agent That Inhibits Gamma-Ray-Induced DNA Breakdown
In previous experiments it was shown that gamma-ray-induced DNA breakdown, which is much enhanced by incubation of the irradiated bacteria in acetate buffer, can be inhibited by a series of metabolites and antimetabolites which, under the same conditions, inhibited DNA. synthesis in the nonirradiated controls. Biosynthesis of both types of nucleic acids and of proteins was studied when one of these inhibitory substances (DNP), which was applied to the bacteria during 90 minutes of postirradiation incubation in acetate buffer, was removed, and the microorganisms were reincubated in a mineral medium. We found that after resuspension in the mineral medium only a very small amount of DNA was slowly broken down. During reincuba-tion the biosynthesis of DNA, RNA, and protein was very slow and limited in amount in comparison with the same biosynthetic processes going on in bacteria incubated in a mineral medium immediately after irradiation. The meanings of the above results are discussed.