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Abstract
Two theories have been previously described that potentially explain how T4 bacteriophage are inactivated using microwave sterilization: thermal and non-thermal effects. In order to investigate the mechanism of inactivation following microwave irradiation, purified T4 bacteriophage were subjected to microwave irradiation for 10, 15, and 20 seconds (thermal effect) and for 10, 20, 30 and 40 seconds while on ice (nono o o thermal effect). In addition, T4 bacteriophage samples were heated to 65 C, 80 C and 95 C for 10 minutes to determine the effect of heat alone. The treated samples were subsequently analyzed via standard bacteriophage plaque assays to determine survival. DNA agarose gel electrophoresis was performed to identify samples with ruptured versus intact capsid and to identify any possible phage DNA mutagenesis due to the treatments. Non-thermal microwave irradiation of T4 phage resulted in minor killing while thermal microwave irradiation showed significant killing, likely due to capsid rupture. External heat showed notable killing as well, though it was likely that the DNA itself was denatured. Although the data presented in this study support the thermal theory of inactivation, the exact mechanism of bacteriophage inactivation following microwave irradiation remains inconclusive.