The effect of reactive oxygen and nitrogen species on lux-biosensors based on the Escherichia coli K12 MG1655 and Salmonella typhimurium LT2 host strains was investigated. The bioactivity of exogenous free radicals to the constitutively luminescent E. coli strain with plasmid pXen7 decreased in the order H2O2 > OCl– > NO• > RОO• > ONOO–> O 2 •- while the bioluminescence of S. typhimurium strain transformed with this plasmid decreased in the order NO• > H2O2 > ONOO– > RОO• > OCl– > O 2 •- The cross-reactivity of induced lux-biosensors to reactive oxygen and nitrogen species, the threshold sensitivity and the luminescence amplitude dependences from the plasmid specificity and the host strain were indicated. The biosensors with plasmid pSoxS′::lux possessed a wider range of sensitivity, including H2O2 and OCl–, along with O 2 •- and NO•. Among the used reactive oxygen and nitrogen species, H2O2 showed the highest induction activity concerning to the plasmids pKatG′::lux, pSoxS′::lux and pRecA′::lux. The inducible lux-biosensors based on S. typhimurium host strain possessed a higher sensitivity to the reactive oxygen and nitrogen species in comparison than the biosensors based on E. coli. .