FIGURE 1 

A proposed common mechanism of killing by bactericidal antibiotics. Antibiotics with diverse targets (ribosome for aminoglycosides, DNA gyrase for quinolone and penicillin-binding proteins for -lactam) trigger NADH depletion and superoxide (O₂^-) formation by hyperactivation of the electron transport chain. Free-radical damage of iron-sulfur clusters releases ferrous ion, inducing the generation of highly destructive hydroxyl radicals 1(OH) and cell death. (Figure courtesy of James J Collins).