Comparison of the Lethal Effects of32P and33P Decay inE. Coliand in Bacteriophages

Abstract

The lethal effects of ³²P and ³³P have been compared for T1 and T4 bacteriophages and for radiation-sensitive and -resistant strains of E. coli. A ³³P decay in either bacteriophage, stored at −196°c, is only about half as likely to be lethal as is a ³²P decay, implying that about half of all ³²P lethalities under these conditions are due to nuclear recoil. At a storage temperature of +4°c the lethal efficiency per decay due to nuclear recoil is about the same as at −196°c, although overall lethal efficiency per decay is considerably higher at +4°c for both isotopes. In the four strains of E. coli tested, B_s−1, K-12 AB2463, K-12 AB1157 and 15THU, all stored at −196°c during decay, there is no evidence for a greater lethal efficiency per decay from ³²P than from ³³P, implying that nuclear recoil is unimportant in ³²P killing of E. coli. A model is proposed which explains the greater sensitivity of bacteriophage to lethality from nuclear recoil by the interruption of transfer of phage DNA into the host cell.