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Determination of a thermal equivalent of millimeter microwaves in living cells
Abstract:
Recent microwave experiments have shown frequency dependent influences on the growth rate of bacteria. To determine whether microwaves are able to affect growth (or to induce lesions in cellular DNA of yeast cells), experiments were performed with millimeter microwaves at frequencies between 70 and 75 GHz. Saccharomyces cerevisiae cells were irradiated on millipore filter discs placed on agar plates in open petri dishes. A diploid strain of yeast (D5, Zimmerman), that is sensitive to genetic insult was used to study the effects of temperature and of microwave irradiation on cell survival, induction of mitotic recombination, and induction of cytoplasmic "petite" mutations. No evidence of altered survival, impaired function, or structural injury was seen at either frequency, even at power densities as high as 60 mW/cm2. Conventional heating had no deleterious effects until temperatures of specimens exceeded 50 degrees C. In addition, two haploid strains of yeast of opposite mating type were compared with respect to temperature and microwave treatment for formation of zygotes. The elevation of temperature due to the microwave treatment at 60 mW/cm2 and 2 mm distance was estimated to correspond to 3 degrees C.
Insights
Millimeter microwaves at 70-75 GHz did not affect yeast cell survival or DNA. This study found no evidence of growth inhibition or genetic damage in Saccharomyces cerevisiae exposed to these frequencies.
Area of Science:
- Biophysics
- Cell Biology
- Microwave Technology
Background:
- Previous studies indicated frequency-dependent effects of microwaves on bacterial growth.
- The potential impact of microwaves on yeast cell DNA and growth requires further investigation.
Purpose of the Study:
- To determine if millimeter microwaves (70-75 GHz) affect yeast cell growth, survival, or induce DNA lesions.
- To assess the impact of microwave irradiation on mitotic recombination and petite mutations in Saccharomyces cerevisiae.
Main Methods:
- Yeast cells (Saccharomyces cerevisiae) were irradiated with millimeter microwaves (70-75 GHz) at power densities up to 60 mW/cm2.
- Assessed cell survival, mitotic recombination, and petite mutations in diploid yeast.
- Compared zygote formation in haploid yeast strains under microwave and conventional heating.
Main Results:
- No significant alterations in yeast cell survival, function, or structure were observed at the tested microwave frequencies and power densities.
- Conventional heating showed no adverse effects until temperatures exceeded 50°C.
- Microwave irradiation at 60 mW/cm2 caused a negligible temperature increase (estimated 3°C).
Conclusions:
- Millimeter microwaves in the 70-75 GHz range do not appear to cause genetic damage or affect the survival of Saccharomyces cerevisiae under the experimental conditions.
- The observed temperature increase from microwave exposure was minimal and unlikely to be responsible for any biological effects.