The transcriptomic response of cells of the thermophilic bacteriumGeobacillus icigianusto terahertz irradiation

ABSTRACT As areas of application of terahertz (THz) radiation expand in science and practice, evidence is accumulating that this type of radiation can affect not only biological molecules directly but also cellular processes as a whole. In this study, the transcriptome in cells of the thermophilic bacterium Geobacillus icigianus was analyzed immediately after THz irradiation (0.23 W/cm 2 , 130 μm, 15 min) and at 10 min after its completion. THz irradiation does not affect the activity of heat shock protein genes and diminishes the activity of genes whose products involved in peptidoglycan recycling, participate in redox reactions and in protection of DNA and proteins from damage, including genes of chaperone protein ClpB and of DNA repair protein RadA as well as genes of catalase and kinase McsB, which play an essential role in the regulation of the cellular response to oxidative stress. Gene systems responsible for the homeostasis of transition metals (copper, iron, and zinc) proved to be the most sensitive to THz irradiation; downregulation of these systems increased significantly 10 min after the end of the irradiation. Blockage of the expression of genes responsible for copper export and iron import systems under the influence of THz irradiation may be a harbinger of toxic stress in G. icigianus cells, which leads to destabilization of the function of proteins containing Fe/S clusters. It was also hypothesized that some negative effects of THz radiation on metabolism in G. icigianus cells are related to disturbances in activities of gene systems controlled by metal-sensitive transcription factors.