Fig. 5. Evolving model for H2S mediated antibiotic tolerance. Bactericidal antibiotics alters respiration and metabolism to elevate the production of endogenous ROS. Based on our findings, we propose that bacterial H2S provides tolerance to antibiotics by two mechanisms; (i) down-regulation of energy-efficient cytochrome bo oxidase (Cyo) and induction of less-energy efficient cytochrome bd oxidase I/II (CydAB/AppBC) to maintain respiratory flux and redox balance, and (ii) augmentation of antioxidant capacity by elevating catalase and superoxide dismutase (SOD) activities. NDH: NADH dehydrogenase and SDH: succinate dehydrogenase.
