The influence of low intensity microwave on some bacterial growth

The action for of low intensity microwaves (power density 10 mW/cm2, frequency of about 10.75 GHz) on growth dynamics was searched in two microbial cultures: Staphylococcus aureus ATCC-6538 (Gram positive bacteria) and Escherichia coli ATCC-10536 (Gram negative bacteria). It was evaluated the number of living cells/ml using a JASCO spectrophotometer for measurements carried out at 3, 6 , 9, 12, 24, 36, 48 and 72 hours in samples and controls. The results obtained revealed a stimulatory effect of microwaves on cell multiplication in both tested bacteria all over the experiment. Statistical computation showed different mathematical functions for experimental graphs approach. Logarithmic function was found to fit to E. coli growth (correlation coefficient equal to 0.978) while exponential function was found to approximate S. aureus dynamics (correlation coefficient equal to 0.758). A low thermal effect could be the main cause of such behaviour, as expected. However, a non-thermal effect could also be involved in the dynamics of these pathogen microorganisms. (authors)