Objective It is necessary to evaluate the harmful or useful effects of electromagnetic waves on living organisms and determine the threshold of these radiations. In this research, the effect of magnetic fields on the growth of gram-positive ( Staphylococcus aureus ) and gram-negative ( Escherichia coli ) bacteria has been evaluated.Results In Gram-negative bacteria such as E. coli in both magnetic fields 1mT and 2mT at different frequencies, an additive effect was seen on the growth of bacteria. When the frequency increased the trend of increasing bacterial growth, slowed. In Gram-positive bacteria such as Staphylococcus, this effect was less. In 1mT magnetic field, the growth of bacteria was seen but the 2mT field was virtually ineffective and the differences between two groups at different frequencies were not significant. Also, significant changes didn't observe with increasing frequency. Study of bacterial growth in terms of frequency in both case and control groups showed an increasing trend. With increasing frequency from 50 Hz to 150Hz significantly increased the rate of bacterial growth and the growth in the higher frequencies more than lower frequencies. Magnetic field had increment effect on the growth of bacteria. This effect was greater on gram-negative than on gram-positive.

Objective: The effects of electromagnetic waves on the growth of living organisms and the determination of the threshold of these radiations have remained elusive. Therefore, in this research, we have investigated the growth rate of gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria that had been exposed to the different frequencies of electromagnetic fields. Results: The more frequency increased the slower bacteria grew; however, in gram-positive bacteria such as S. aureus, this effect was seen less. The effect of the 1mT electromagnetic field in the growth of S. aureus was significant between the two groups, nonetheless, in the 2mT electromagnetic field, the effect was not significant between the two groups at different frequencies. Noteworthy, no significant change was observed by increasing the frequency in S. aureus exposed bacteria in comparison to the control group. The study of bacterial growth in terms of frequency in both case and control groups showed an increasing trend. Increasing the frequency from 50 Hz to 150Hz, significantly, enhanced the rate of bacterial growth. On the whole, the magnetic field had an increment effect on the growth of bacteria; in fact, this effect was greater on the gram-negative than on the gram-positive bacteria.