This is a report on the antibacterial activity of ZnO and CuO nanoparticles synthesized via sol-gel method. The studies were performed on Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli and Pseudomonas aeruginosa bacteria using disc and well diffusion methods, bioluminescence and optical density analysis. The results show a strong decline of bacterial strains after a short contact with nanoparticles. The modelling allowed clarifying the bacterial sensitivity of toxic agents at different stages of their population evolution kinetics. It was concluded that the bacterial suppression is most effective at the exponential growth phase while it is of a lower effectiveness at the lag and stationary phases. The CuO and ZnO nanoparticles showed comparable effectiveness at the exponential growth phase. In the same time, ZnO was almost inactive at the lag phase and of lower effectiveness at the stationary phase, at which CuO conserved a significant activity.