Abstract
Several radiation sources were used to irradiate E. coli WP-2. Radiations were: 140-Mev oxygen ions 40 Mev [alpha] particles, 1 Mev electrons, gamma rays, and 250kvp X-rays. Cell survival and reversion of tryptophan independence were studied. At doses giving common survival fractions, there are about half as many reversions for the oxygen ions as for the other radiations. Complete curves for survival and reversion as a function of radiation dose are presented. The effect of irradiating in N2 versus irradiation in air was studied for survival and reversion to tryptophan independence. For survival, the N2 protection is equivalent to a factor of about 3.5 for X-rays and 1.5 for oxygen ion irradiation. For reversion to tryptophan independence, this effect is about 1.7 for X-rays and 1.3 for oxygen ion irradiation.