This is the first study to present data on the genotoxicity of low γ-irradiation doses for E. coli and S. typhimurium cells obtained using the SOS chromotest and the Ames test. The most pronounced effect was recorded in the first 24 h of γ-irradiation. After 72 h in the Ames test and after 96 h in the SOS chromotest, a significant effect of γ-irradiation on bacterial cells was detected. The absence of genotoxicity at the later stages can be explained by the adaptation of bacterial cells to the conditions of exposure. The findings allow the bacterial test system to be used for studying the effects of low doses at the early stages of exposure to radiation.