Fig. 4. ZnONP induced cell death, reactive oxygen species, and inhibition of cellular respiration in treated clinical isolates. The ZnONP (1.0 mg ml^–1) mediated increase in the number of dead cells as a result of increased membrane permeability. Panels A and C show the residual fluorescence of PI in K. pneumoniae and S. aureus cells. Panel C and D present an increase in PI fluorescence due to the damaged cell membrane. Panels E and G show the residual fluorescence of DCF in K. pneumoniae and S. aureus cells. Panel F and H show a significant increase in intracellular ROS when exposed to 1 mg ml^–1 of ZnONPs. Panel I shows the inhibition of cellular respiration of E. coli, S. aureus, K. pneumoniae, and P. aeruginosa by green synthesized ZnONPs at 0.125–1.5 mg ml^–1. The decrease in red color intensity in microtitre wells represents the loss of metabolic activity of bacterial cells.