Effects of microwave irradiation on some membrane-related processes in bacteria.

In a series of experiments performed on intact cells or spheroplasts of E. coli and Bac. subtilis a possibility of non-thermal effects induced by continuous microwave irradiation of a low power density (at wave length range from 0.0 to 7.8 mm) was studied. Thymidine and thymine uptake, leakage of potassium and hydrogen ions as well as the uptake of the transforming DNA by the component cells of Bac. subtilis were shown to be affected in a way typical of that due to heating of a sample. No specific dependence of the effects observed on wavelength was found.

Thymidine uptake in bacteria: the effect of purine nucleosides.

The kinetics of thymidine uptake by Escherichia coli and Bacillus subtilis cells in the presence of adenine and guanine nucleosides was investigated. The initial concentration of thymidine in the growth medium was 0.35 microng/ml while the initial concentration of purine nucleosides ranged from 25 to 250 microng/ml. Adenine nucleosides when present at a concentration more than 50 microng/ml strongly inhibit thymidine uptake by the bacteria. The duration of the inhibition depends on the initial concentration of adenine nucleoside in the growth medium. At an initial concentration of deoxyadenosine (or adenosine) of 250 microng/ml the time of inhibition of thymidine uptake was about 60 min. During this period thymidine is almost completely preserved from the action of bacterial thymidine phosphorylase. Guanine nucleosides (guanosine or deoxyguanosine) do not markedly inhibit thymidine uptake by bacteria even at a concentration of 250 microng/ml. It is shown that they do protect thymidine from the phosphorolytic action of the thymidine phosphorylase although much less effectively than adenine nucleosides. It is suggested that some areas in the bacterial membrane where thymidine phosphorylase is located are not available to guanine nucleosides.