E. coli aggregation and impaired cell division after terahertz irradiation.

In this study we demonstrated that exposure of Escherichia coli (E. coli) to terahertz (THz) radiation resulted in a change in the activities of the tdcABCDEFGR and matA-F genes (signs of cell aggregation), gene yjjQ (signs of suppression of cell motility), dicABCF, FtsZ, and minCDE genes (signs of suppression of cell division), sfmACDHF genes (signs of adhesin synthesis), yjbEFGH and gfcA genes (signs of cell envelope stabilization). Moreover, THz radiation induced E. coli csg operon genes of amyloid biosynthesis. Electron microscopy revealed that the irradiated bacteria underwent increased aggregation; 20% of them formed bundle-like structures consisting of two to four pili clumped together. This could be the result of changes in the adhesive properties of the pili. We also found aberrations in cell wall structure in the middle part of the bacterial cell; these aberrations impaired the cell at the initial stages of division and resulted in accumulation of long rod-like cells. Overall, THz radiation was shown to have adverse effects on bacterial populations resulting in cells with abnormal morphology.

Fluorescent bacterial biosensor E. coli/pTdcR-TurboYFP sensitive to terahertz radiation.

A fluorescent biosensor E. coli/pTdcR-TurboYFP sensitive to terahertz (THz) radiation was developed via transformation of Escherichia coli (E. coli) cells with plasmid, in which the promotor of the tdcR gene controls the expression of yellow fluorescent protein TurboYFP. The biosensor was exposed to THz radiation in various vessels and nutrient media. The threshold and dynamics of fluorescence were found to depend on irradiation conditions. Heat shock or chemical stress yielded the absence of fluorescence induction. The biosensor is applicable to studying influence of THz radiation on the activity of tdcR promotor that is involved in the transport and metabolism of threonine and serine in E. coli.

Study on the effects of terahertz radiation on gene networks of Escherichia coli by means of fluorescent biosensors.

Three novel fluorescent biosensors sensitive to terahertz (THz) radiation were developed via transformation of Escherichia coli (E. coli) cells with plasmids, in which a promotor of genes matA, safA, or chbB controls the expression of a fluorescent protein. The biosensors were exposed to THz radiation from two sources: a high-intensity pulsed short-wave free electron laser and a low-intensity continuous long-wave IMPATT-diode-based device. The threshold and dynamics of fluorescence were found to depend on radiation parameters and exposure time. Heat shock or chemical stress yielded the absence of fluorescence induction. The biosensors are evaluated to be suitable for studying influence of THz radiation on the activity of gene networks related with considered gene promoters.

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

The mutagenicity and genotoxicity in bacteria of 2.3THz radiation (THz) produced by a free-electron laser (NovoFEL) were evaluated; exposures were 5, 10, or 15min at average power 1.4W/cm(2). 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 15min exposure, and an increase in ß-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 (8µM; positive control) and THz exposure (5min) on genotoxicity in E.coli PQ37. Unexpectedly, THz radiation decreased 4-NQO genotoxicity.

Studying the non-thermal effects of terahertz radiation on E. coli/pKatG-GFP biosensor cells.

Studies of the impact of terahertz radiation on living objects present a significant interest since its use for security systems is currently considered promising. We studied the non-thermal impact of terahertz radiation on E. coli/pKatG-gfp biosensor cells. The Novosibirsk free electron laser (NovoFEL), which currently has the world's highest average and peak power, was used as the source of terahertz radiation. We demonstrated that exposure to terahertz radiation at the wavelengths of 130, 150, and 200 µm and a power of 1.4 W/cm(2) induces changes in green fluorescent protein (GFP) fluorescence values and thus induces the expression of GFP in E. coli/pKatG-gfp biosensor cells. Possible mechanisms of the E. coli response to non-thermal exposure to terahertz radiation are discussed.