Pathogen-induced colitis increases the availability of host-derived respiratory electron acceptors to increase pathogen abundance in the colon. (A) During homeostasis, oxygen (O2)-consuming reactions maintain the colonic epithelium in a state of physiological hypoxia. (B) During Salmonella infection, invasion of the intestinal mucosa by the pathogen triggers transepithelial migration of neutrophils, resulting in a depletion of Clostridia and loss of epithelial hypoxia. NO, nitric oxide; ROS, reactive oxygen species; NO3−; nitrate; S2O32−, thiosulfate; H2S, hydrogen sulfide, S4O62−, tetrathionate; CO2, carbon dioxide; Arg, arginine. Created with BioRender.com.