Cellular effects in microbial tester strains caused by exposure to microwaves or elevated temperatures
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Abstract:
Several tester strains of Salmonella typhimurium, TA-98, TA-100, TA-1535, and TA-1538; Escherichia coli, W3110 (pol A+) and p3438 (pol A-, repair deficient); and Saccharomyces cerevisiae, D3, D4, and D5 were tested for lethal and mutagenic events when exposed to elevated temperatures or to x-band, pulsed microwave radiation at various power densities. When compared to E. coli pol A+ under growing conditions, E. coli pol A- exhibited decreased cell growth when exposed to microwave radiation at power levels at or above 20 mW/cm2 as well as to temperature levels above 42 degrees C. All yeast and other bacterial strains showed cellular lethality at similar microwave intensities and elevated temperatures. When exposed to elevated temperatures in saline, both quiescent yeast and Salmonella strains exhibited lethal events. However, the Salmonella strains tested showed comparatively less induction of genetic events in the quiescent state compared to induction when the cell were actively growing in broth. These results demonstrate that elevated temperatures generated by microwave exposure could produce genetic events in microbial assay systems. If such systems are to be of value in examining the nonthermal genetic potential of microwave radiation, careful control over exposure conditions will be required to eliminate heat-induced genetic events.
Insights
Microwave radiation and elevated temperatures can cause cell death and genetic mutations in microbial systems. Careful control of heat is essential when studying non-thermal microwave radiation effects.
Area of Science:
- Microbiology
- Genetics
- Biophysics
Background:
- Microbial assay systems are used to detect mutagenic and lethal events.
- Understanding the effects of environmental stressors like temperature and radiation is crucial.
Purpose of the Study:
- To investigate the lethal and mutagenic effects of microwave radiation and elevated temperatures on various microbial strains.
- To differentiate between thermal and non-thermal effects of microwave radiation.
Main Methods:
- Exposure of Salmonella typhimurium, Escherichia coli (pol A+ and pol A-), and Saccharomyces cerevisiae strains to x-band microwave radiation and elevated temperatures.
- Assessment of cellular lethality and genetic events under different conditions (growing vs. quiescent state, saline vs. broth).
Main Results:
- Escherichia coli pol A- showed decreased growth at microwave power densities ≥ 20 mW/cm² and temperatures > 42°C.
- All tested yeast and bacterial strains exhibited cellular lethality at similar microwave intensities and elevated temperatures.
- Salmonella strains showed fewer genetic events in the quiescent state compared to actively growing cells.
Conclusions:
- Elevated temperatures induced by microwave exposure can cause genetic events in microbial systems.
- Accurate assessment of non-thermal microwave radiation effects requires controlling and eliminating heat-induced genetic events.