ABSTRACT
Biological effects of extremely low frequency [ELF] pulsed electromagnetic fields have become attractive for research but still the mechanisms for this effects are not known. Moreover some reported biological effects of ELF are questionable due to poor reproducibility of the experiments. In this project ELF pulsed and DC magnetic fields were investigated on the growth rate of E. Coli DH5-alpha. In this experimental study, The cells were cultured in a lactose defined medium divided into two groups of 5 cuvetts and then were incubated. The experimental group was then placed in the field while the control group was left with no field. The applied fields were pulsed 6 msec apart and different frequency ranges from 10 to 45 Hz with the increment of 5 Hz and effective field range of 2 to 4 mT with an increment of 1mT and a constant field of 1mT through out the experiment. The growth rate was studied with turbidometery by spectrophotometers in the specified time interval. The growth rates in logarithmic phase and lag time were evaluated. The results indicated that pulse and DC combined magnetic fields increase the growth rate except in 15, 25 and 40 Hz frequencies. Lag time doesn't change in 15, 30 and 45 Hz frequencies. But in 20 and 40 Hz frequencies, magnetic field causes on increase and in 10, 25 and 45 Hz frequencies maximum decreases lag time. So in this frequency range, the magnetic field effect on the lag time has been repeated at an interval of 15 Hz. This research shows the existence of certain frequency windows for the resonance of the effects of the magnetic field on growth the cell