The Synthesis of DNA by Membrane-DNA Complexes from E. Coli B/r and B s−1 after Exposure to Fast Electrons and Neutrons: The Measurement of Oxygen-enhancement Ratios and RBE Values

SummaryIrradiation of E. coli B/r and Bs−1 depressed the DNA synthetic activity of the DNA-membrane complexes from these bacteria. The depression of this activity in both strains in the presence of oxygen was seven to eight times greater than under anoxic conditions when irradiation was with fast electrons. The oxygen-enhancement ratios for neutrons were 4·0 and 5·2 for E. coli B/r and E. coli Bs−1, respectively.The DNA-synthesizing abilities of complexes from the radiation-resistant E. coli B/r and the radisation-sensitive E. coli Bs−1 were equally inhibited by electron irradiation, but with fast neutrons the synthetic activity of the DNA-membrane complex from E. coli B/r was more inhibited than that from E. coli Bs−1.