The investigation had the purpose to study the lethal effect of laser infrared radiation (1220-1320 nm) on various genotypes of E. coli K-12 cells. Laser was produced by a parametric LiNbO3 light generator pumped up by the NdYAG second harmonic radiation. Results were compared with effects of X-ray radiation at 200 kV. The irradiated bacteria were cultivated in a solid full nutrient medium over 24 hrs at 37 degrees C. Bacteria spread in monolayer on the surface of "starvation" agar (4% agar-agar) were exposed to each type of radiation at room temperature. Survivability of the cells was determined by counting macrocolonies after 2 days of growth at 37 degrees C. Laser radiation at a wave-length of 1270 nm was found to have the highest lethal effect. This corresponds to one of the peaks of molecular oxygen consumption. Based on comparative analysis of the lethal effectiveness, the bacterial strains revealed equal relative sensitivity to the laser and X-ray radiation. Laser effectiveness was power dependent. Hence, proof has been exhibited that laser radiation at a wave-length of 1270 nm can be used as a bactericide means. The apparent advantage of the means over the photodynamic therapy is that no dyes are required.
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