UC Davis

The colonic microbiota exhibits cross-sectional heterogeneity, but the mechanisms that govern its spatial organization remain incompletely understood. Here we used Citrobacter rodentium, a pathogen that colonizes the colonic surface, to identify microbial traits that license growth and survival in this spatial niche. Previous work showed that during colonic crypt hyperplasia, type III secretion system (T3SS)-mediated intimate epithelial attachment provides C. rodentium with oxygen for aerobic respiration. However, we find that prior to the development of colonic crypt hyperplasia, T3SS-mediated intimate attachment is not required for aerobic respiration but for hydrogen peroxide (H₂O₂) respiration using cytochrome c peroxidase (Ccp). The epithelial NADPH oxidase NOX1 is the primary source of luminal H₂O₂ early after C. rodentium infection and is required for Ccp-dependent growth. Our results suggest that NOX1-derived H₂O₂ is a resource that governs bacterial growth and survival in close proximity to the mucosal surface during gut homeostasis.