PHOTOREVERSAL OF ULTRAVIOLET-INDUCED MUTAGENIC AND LETHAL EFFECTS IN ESCHERICHIA COLI

Abstract

The lethal and the mutagenic effects of exposure of E. coli B/r to low doses of 2537 A (ultraviolet) were greatly reduced by post-treatment with light. The mutagenic effect of high doses (2500 ergs per sq. mm., or more) was stable and only the lethal effect could be reversed. Further, the proportion of mutations obtained from u.-v. treatment alone was approx. the same for all doses from 500 to 5000 ergs/sq. mm. It is believed that a photosensitive and a photostable mutagen-poison are formed within the cell by the u.-v., and that likelihood of mutation is constant for quantities for mutagen-poison above a critical level. When the stable poison is present in quantities above this level, loss of the unstable poison can affect survival but not mutation.