|
Vol 48(2014) N 6 p. 870-877; DOI 10.1134/S0026893314060107 V.Yu. Kotova, A.S. Mironov, G.B. Zavilgelsky* Role of reactive oxygen species in the bactericidal action of quinolones as inhibitors of DNA gyrase State Research Center GosNIIGenetika, Moscow, 117545 Russia*zavilgel@genetika.ru Received - 2014-05-21; Accepted - 2014-06-16 Quinolone antibiotics inhibit DNA gyrase, but the induced degradation of chromosomal DNA is determined by a complex process of the joint action of quinolones and hydroxyl radical, OH'. In this study, we used inducible specific lux biosensors, i.e., Escherichia coli bacteria containing hybrid plasmids pColD'::lux, pSoxS'::lux, and pKatG'::lux, to quantify the level of stress responses and their time dependence in bacterial cells. Quinolones (nalidixic acid and norfloxacin) were shown to induce SOS response and oxidative stress with the formation of superoxide anion O2- in Escherichia coli cells. The main parameters of SOS response and oxidative stress, which depend on the quinolone concentration, were determined. The formation of superoxide anion occurred almost simultaneously with the SOS response. The mutant strain E. coli sodA sodB, which contains no active forms of superoxide dismutases SodA and SodB is characterized by an increased resistance to quinolones compared to wild-type cells. At high concentrations of quinolones (>20µg/mL nalidixic acid and >500 ng/mL norfloxacin), their bactericidal effect is partially caused by the conversion of the superoxide anion to hydrogen peroxide H2O2 conducted by superoxide dismutases SodA and SodB, which is followed by the Fenton reaction and the formation of toxic hydroxyl radical OH'. At low concentrations of quinolones (<20 µg/mL nalidixic acid and <500 ng/mL norfloxacin), the contribution of the reactive oxygen species in the antimicrobial effect is negligible. quinolone, fluoroquinolone, reactive oxygen species, lux biosensor |