2.3 THz radiation: Absence of genotoxicity/mutagenicity in Escherichia coli and Salmonella typhimurium

• Genotoxicity and mutagenicity of THz radiation were studied in two bacterial tests.
• Ames test showed THz radiation effect on total cell number but not mutagenic effect.
• Normalized β-galactosidase activity indicated no genotoxicity in SOS chromotest.
• SOS chromotest data imply that THz radiation may affect DNA-protein interactions.
• Both tests revealed THz radiation effect on cell metabolism and measured parameters.

The mutagenicity and genotoxicity in bacteria of 2.3 THz radiation (THz) produced by a free-electron laser (NovoFEL) were evaluated; exposures were 5, 10, or 15 min at average power 1.4 W/cm2. Two Ames mutagenicity test strains of Salmonella typhimurium, TA98 and TA102, were used. For the genotoxicity test, we measured SOS induction in Escherichia coli PQ37. No significant differences were found between exposed and control cells, indicating that THz radiation is neither mutagenic nor genotoxic under these conditions. Nevertheless, a small increase in total cell number of S. typhimurium after 15 min exposure, and an increase in β-galactosidase and alkaline phosphatase activities in E.coli PQ37, were observed, indicating some effect of THz radiation on cell metabolism. We also examined the combined effect of 4-NQO (8 μM; positive control) and THz exposure (5 min) on genotoxicity in E.coli PQ37. Unexpectedly, THz radiation decreased 4-NQO genotoxicity.