Low-power infrared laser on survival, proliferation, and reactive oxygen species levels in Escherichia coli cultures

Laser devices are light sources that emit monochromatic, coherent, and collimated electromagnetic radiation beams. Low-power lasers are widely used to treat clinical conditions based on the photobiomodulation effect. Despite therapeutic applications, mainly in continuous waves, limited data are available on photobiomodulation effects induced by low-power lasers in the pulsed emission mode. Thus, the aim of this study was to evaluate the effects of a low-power pulsed infrared laser on survival, proliferation, DNA damage, and reactive oxygen species (ROS) levels in Escherichia coli cells. E. coli C600 cultures and pUC19 plasmids were exposed to a low-power pulsed (5000 Hz) infrared (904 nm) laser (1.1, 2.3, and 4.6 J). Bacterial survival was evaluated by survival fractions, bacterial proliferation was evaluated by measurement of bacterial colony areas, DNA damage was evaluated by plasmid profiling in agarose gels after electrophoresis, and ROS level was evaluated by flow cytometry. The results suggest that exposure to a low-power infrared laser in pulsed emission mode does not alter the proliferation of E. coli C600 and the electrophoretic profile of bacterial plasmids but decreases survival and increases ROS levels in E. coli C600 cultures.