Correlation of Bacterial Sensitivities to Ionizing Radiation and Mild Heating

DNA, isolated from bacteria which had been heated to 520 for several minutes, sedimented in an alkaline sucrose gradient more rapidly than DNA from untreated bacteria, in a similar manner to DNA from bacteria exposed to ionizing radiation. There is a general correlation between the sensitivities to γ- radiation and to incubation at 520 of various strains of Escherichia coli. Heated bacteria were more sensitive to subsequent exposure to γ-radiation, indicating that recovery capacity was itself heat-sensitive. The normal function of some of the cellular systems conferring radiation resistance might therefore be the mitigation of DNA damage due to mild thermal stress at elevated and perhaps also at normal temperatures.