Induction of Provariants as a Function of Dose of Ultraviolet Radiation: With an appendix on the contribution of differential effects upon survival of provariant and nonvariant spores in the modifications of induced variant frequency resulting from post-irradiation treatments

Abstract

SUMMARY: With spores of Streptomyces sp. strain T12 irradiated at doses of ultraviolet light up to 1000 ergs/mm.2 and then incubated in distilled water, both the proportion of survivors and the proportion of induced variants amongst the survivors rose progressively to maximal values as the period of incubation was increased. The maximal proportion of variants was attained before the maximal proportion of survivors. The rate of increase of survival and the final level of survival were enhanced in the presence of iodoacetate. The rate of increase of variant frequency was enhanced by iodoacetate. but the maximal proportion of variants was not raised. The changes of variant frequency resulting from post-irradiation treatments do not appear to be due to selectively greater increases in the survival of variant spores than of non-variant spores.