SummaryThe X-ray sensitivity of E. colt is reduced if the cells are irradiated in the presence of certain chemical agents. BAL, ethanol, and sodium hydrosulfite increase the dose required to kill a given number of cells in suspensions at 2°C by a factor of 3-4. Other sulfhydryl compounds, glycols, and low-molecular-weight alcohols also increase the survival of E. coli suspensions.