Figure 4.

Pathogens exploit microbiota-generated metabolites. Bacteroides thetaiotaomicron cleaves host mucin producing monosaccharides, including fucose and sialic acid. (A) Normally, the commensal bacteria consume these nutrients, preventing their consumption by pathogens. (B) If the microbiota is depleted or disturbed, such as after antibiotic use, pathogens are able to utilize these nutrients to establish infection. (C) Pathogens, such as Salmonella, take advantage of molecules generated by the host inflammatory response. Salmonella induces inflammation, which leads to the production of superoxide (O₂⁻) and iNOS, which in turn lead to the formation of tetrathionate (S₄O₆²⁻) and nitrate (NO₃⁻), respectively. Salmonella utilizes tetrathionate and nitrate as electron acceptors during anaerobic respiration.