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  • Title: Effect of 99 GHz continuous millimeter wave electro-magnetic radiation on E. coli viability and metabolic activity.
    Author: Cohen I, Cahan R, Shani G, Cohen E, Abramovich A.
    Journal: Int J Radiat Biol; 2010 May; 86(5):390-9. PubMed ID: 20397844.
    Abstract:
    PURPOSE: To investigate time exposure dependence of continuous millimeter wave (CW) 99 GHz radiation on Escherichia coli bacterial cell viability and metabolic activity. MATERIALS AND METHODS: Suspensions of E. coli bacterial cells with an optical density of OD(660 nm) = 0.1 were used for viability tests and OD(660 nm) = 1.0 for metabolic activity tests. These suspensions were exposed to 99 GHz CW electromagnetic radiation, generated by a Backward Wave Oscillator (BWO) tube base instrument with a horn antenna at the BWO exit, to obtain an almost ideal Gaussian beam. Calculations of the Gaussian beam show that a power of 0.2 mW/cm(2) was obtained at the bacterial plane. RESULTS: The experimental results show that 1 hour of exposure to 99 GHz CW electromagnetic radiation had no effect on E. coli viability and colony characterisation. In 19 h of radiation, the number of colonies forming units was half order of magnitude higher than the sham-exposed and the control. However, 19 h of exposure did not affect the E. coli metabolic activity. CONCLUSIONS: Exposure of E. coli to millimeter wave (MW) CW 99 GHz radiation for a short period did not affect the viability of E. coli bacterial cells. However, exposure for 19 h caused a slight proliferation but did not influence the metabolic activities of about 90 biochemical reactions that were examined. Hence, we assume that the slight proliferation (half order of magnitude) after 19 h of exposure dose not have a biological meaning.
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