Figure 6.
Microbial-derived signals deplete local O2. The top panels depict hypoxia localization (red ), illuminated by the nitroimidazole dye pimonidazole, in (a) germ-free and (b) conventional animals. DAPI stains (blue) indicate areas of high DNA concentration. (c) A model in which microbial-derived short-chain fatty acids (e.g., butyrate) stimulate epithelial metabolism and deplete intracellular O2 to the extent that HIF-1α is stabilized and promotes epithelial barrier function. Abbreviation: HIF, hypoxia-inducible factor.