Radiofrequency transmission line for bioluminescent Vibrio sp. irradiation

Abstract

We present the study and the analyses of a transmission line for radiofrequency (RF) irradiation of bacteria belonging to Vibrio harveyi-related strain PS1, a bioluminescent bacterium living in symbiosis with many marine organisms. The bioluminescence represents a new biologic indicator which is useful for studying the behaviour of living samples in the presence of RF waves due to the modern communication systems. A suitable transmission line, used as an irradiating cell and tested up to the maximum frequency used by the global system for mobile communications and universal mobile telecommunications system transmissions, was characterized. In this experiment, the RF voltage applied to the transmission line was 1 V. Due to short dimensions of the line and the applied high frequencies, standing waves were produced in addition to progressing waves and the electric field strength varies particularly along the longitudinal direction. The magnetic field map was not strongly linked to the electric one due to the presence of standing waves and of the outgoing irradiation. RF fields were measured by two homemade suitable probes able to diagnostic fields of high frequency. The field measurements were performed without any specimens inside the line. Being our sample made of living matter, the real field was modified and its value was estimated by a simulation code. The bioluminescence experiments were performed only at 900 MHz for two different measured electric fields, 53 and 140 V/m. The light emission was measured right from the beginning and after 7 and 25 h. Under RF irradiation, we found that the bioluminescence activity decreased. Compared with the control sample, the diminution was 6.8% and 44% after 7 and 25 h of irradiation, respectively, both with the low or high field. No changes of the survival factor for all the samples were observed. Besides, to understand the emission processes, we operated the deconvolution of the spectra by two Gaussian curves. The Gaussian peaks were approximately centered at 460 nm and 490 nm. The 490 nm peak was higher than the control one. Under RF, the 490 nm peak decreased compared to the 460 nm one. The decreasing was stronger for the sample in the higher field. The ratio of the emission area of the 490 nm to 460 nm was 5 for the control sample. It decreased up to 1.6 for the samples under RF. The bioluminescence improves the DNA repair by photoreactivation, and there is evidence that photolyase is preferentially activated by blue/violet light. Our finding suggests that RF exposure may stimulate DNA repair by shifting the emission spectra from blue/green (490 nm) to blue/violet (460 nm).