Anoxic Radiosensitization of TwoBacillusSpecies by P-nitroacetophenone

Abstract

P-nitroacetophenone (PNAP) has been tested for its ability to alter radiation sensitivity in two closely related Bacilli. PNAP is an anoxic sensitizer of spores and vegetative cells of both B. megaterium and B. pumilus, although the extent of PNAP's sensitization differs in each of the four test systems. In the spores, PNAP increased the anoxic responses by 40 per cent in B. megaterium and 20 per cent in B. pumilus. (The oxygen enhancement ratios here are 2·14 and 2·22 respectively.) In both vegetative cells, PNAP achieved full oxygen-level sensitization, increasing the anoxic responses of B. megaterium by 130 per cent and B. pumilus by 60 per cent. These factor-of-two ratios in PNAP's efficiency in both the spores and vegetative cells suggest this difference might be due to inherent differences in the cells themselves. We find that the ratios of the amounts of DNA in the spores and vegetative cells correspond closely to the ratios of PNAP's maximum efficiencies in these cells. These results, while not identifying DNA as the target, suggest that specific reactions between PNAP and possible target molecules should be studied. In this way, the target, and subsequently the mechanism for PNAP's sensitization, might be discovered.