The Action of Ionizing Radiation on Postirradiation Synthesis and Degradation of DNA in Escherichia coli 15 T - L -

Abstract

The effect of ionizing radiation on the synthesis and degradation of DNA in E. coli 15 T-L- has been studied. Synthesis continues for low doses for about a division time, but the greater the dose is, the lower the rate. There is a dose-reduction factor of 2 for the action on synthesis between oxygenated and nitrogenated medium. Degradation of DNA is observed in E. coli 15 T-L-, WWU, B and B/r strains. The dose-effect relationship for degradation has been established for normal cells, both oxygenated and nitrogenated, and for cells with 5-BU in the DNA. In the latter case degradation occurs at smaller doses than for normal DNA. DNA synthesized after irradiation does not degrade as readily as normal DNA. Cells heated to 70[degree]C for 10 minutes show no DNA degradation after irradiation. No evidence of cell lysis was found.