Different effects of microwaves and conventional heating on bacteriophage and proliferation in E. coli

Abstract

The proliferation of bacteriophage λ in E. coli was used as a model to compare the effects of microwaves and conventional heating on cell metabolism. Irradiation was carried out in a single-mode focused reactor at 2.45 GHz, under an absorption rate of 0.8±0.1 W/g and at constant temperature (33°C or 37°C). The kinetic curve of phage release from cells irradiated at 37°C was decreased as compared to the control, but significantly increased at 33°C. This was attributed to local overheating of cells by microwaves. Based on the conventional heating experiments, performed at 33°C, 37°C, 41°C and 45°C, we estimated that microwave-induced overheating inside cells was between 4°C and 8°C. However, this should have a limited effect on virus proliferation at 33°C, contrary to the obtained results. The increased expression of heat shock proteins (HSP) was proposed to be responsible for the observed effect of microwaves on virus proliferation.