Investigation of copper nanoparticles antibacterial mechanisms tested by luminescent Escherichia coli strains

The electrostatic interaction between positively charged copper nanoparticles aggregates (ζ = +15.9 ± 8.63 mV) and negatively charged surface of E. coli K12 TG1 cells (ζ = -50.0 ± 9.35 mV) has been established. The time-dependent decline of bacterial cells zeta potential and the coupled inhibition of constitutive bioluminescence level are the results of this interaction. The development of oxidative stress, probably defined by the electron transfer from the cytoplasmic membrane respiratory chains through membrane-integrated copper nanoparticle to the molecular oxygen, is shown as luminescence induction in superoxide- and peroxide-inducible E. coli K-12 MG1655 pSoxS::lux and pKatG::lux reporter strains. The final result of this process, which is responsible for the development of the bactericidal effect of copper nanoparticles, is DNA damage by active oxygen species detected by SOS-inducible E. coli pRecA::lux luminescent strain.