STIMULATING EFFECTS OF MODULATED 150-MHZ ELECTROMAGNETIC-FIELDS ON THE GROWTH OF ESCHERICHIA-COLI IN A CAVITY RESONATOR

A simple and quick screening method is described for investigating the effects of modulated and unmodulated 150 MHz electromagnetic fields o n the growth of Escherichia coli. The experiments were performed in a cavity resonator which allowed simultaneous monitoring of the influenc e of five different field intensities. The impact of temperature fluct uations and the way in which they were taken into account in the exper imental set-up are discussed. Screening was performed at modulation fr equencies of 72,217 and 1100 Hz and also with unmodulated electromagne tic fields. Maximum field values of 1.6 kV m(-1) for the electrical fi eld and 5.4 mu T for the magnetic induction were applied. Cells exhibi ted identical growth behaviour with the various modulation frequencies and in unmodulated fields. Therefore, the modulation frequency could not be responsible for the observed growth effect. Frequency or intens ity windows were not observed. There are hints that the growth stimula tion observed at higher field intensities is partly caused by a microt hermal effect on the cellular level and not by a general temperature i ncrease of the suspending medium.