FIG 2.

A DSS-induced increase in epithelial oxygenation promotes aerobic growth of E. coli. Mice received TUDCA daily by oral gavage. One day after the first TUDCA treatment, mice received drinking water containing 3% DSS. Two days after the beginning of DSS treatment, mice were inoculated with commensal E. coli indicator strains (i.e., with a 1:1 mixture of E. coli Nissle 1917 wild type and an isogenic cydA appA mutant). Organs were collected 4 or 8 days after the beginning of DSS treatment. (A) Transcript levels of the indicated UPR markers were determined in RNA isolated from the colonic epithelium using quantitative real-time PCR. (B) Colon length was determined at necropsy. (C and D) Histopathological scoring of blinded colonic sections was performed by a veterinary pathologist. The histopathological score for each animal (bar) is shown. Representative images of H&E-stained colonic sections are shown. (E) The fitness advantage conferred by aerobic respiration was assessed by determining the competitive index (CI) of E. coli wild type and a cydA appA mutant recovered from colon contents. For data in panels A, B, and E, bars represent geometric means ± standard errors. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001; ns, not statistically significantly different.