Radiosensitization with iodine compounds. 3. Macromolecular synthesis and repair in Bacillus subtilis irradiated in the presence of iodoacetic acid, potassium iodide or potassium iodate.

Abstract

SummaryThe synthesis of DNA, RNA and protein, and the rejoining of DNA strand-breaks and DNA breakdown were studied in cells of Bacillus subtilis γ-irradiated in the presence of iodoacetic acid (I. CH2. COOH), potassium iodide (KI) or potassium iodate (KIO3). Observations on incorporation of radioactive precursors into bacteria mildly radiosensitized by the above reagents indicated that synthesis of DNA was generally more sensitive than that of protein or RNA. A cellular radiosensitizing effect cannot be explained by increase of radiation-induced in situ damage in DNA, because a drug effect was not found on radiation inactivation of transforming DNA. Also, the number of radiation-induced breaks in DNA strand studied by means of alkaline-sucrose gradient centrifugation was very similar in the absence or presence of reagent at the time of irradiation.Studies with KIO3 have shown that the presence of the reagent during irradiation of bacteria considerably reduced rejoining of DNA strand-breaks during subsequ...