Combined Effects of Circularly Polarized Microwaves and Ethidium Bromide on E. coli CELLS

Abstract

The significant difference in the effects of right- and left-handed polarized microwaves of millimeter range (MMW) on Escherichia coli cells and rat thymocytes has been shown previously. The helicity of DNA and supercoiling of DNA loops was suggested to cause the observed dependence of effects on polarization. It is known that DNA intercalators such as ethidium bromide (EtBr) are able to change the supercoiling of DNA loops and to affect the DNA helicity. In the present work, the combined effects of EtBr (1 μg/ml) and circularly polarized microwaves were studied in E. coli cells K12 AB1157 at the stationary stage of growth. The method of anomalous viscosity time dependencies (AVTD) was used to measure changes in the conformation of the genome. The cells were exposed to microwaves at 51.755 GHz and 0.1 mW/cm² for 10 min. Under these conditions of exposure, left-handed microwaves induced changes in the genome conformation, whereas right polarization was almost ineffective. The incubation of cells with EtBr inverted the effective polarization, and right–handed MMW became more effective than left polarization. The data obtained provide new evidence that DNA is a target of MMW effects on cells.