Figure 3. Nitrate respiration enhances luminal growth of EcN during inflammation.

(A-D) Bovine ligated ileal loops treated with thapsigargin or mock-treated (vehicle) were inoculated with a mixture of EcN (WT) and a nitrate respiration-deficient mutant (narG napA narZ). Samples were collected 8 hours after inoculation. (A) Representative H&E stained ileal sections. Scale bar, 200 μm. (B) Combined histopathology score in the ileum. Each dot represents data from an individual animal. (C) Fluid accumulation in ligated ileal loops. (D) Competitive indices (CI) recovered from the luminal fluid (open bars) or mucus scrapings (closed bars). (E-H) DSS-treated mice were inoculated either with EcN (WT) or with the narG napA narZ mutant. Inflammation in the colon (E, F and G) and bacterial numbers recovered from colon contents (E) were determined 5 days after inouclation. (E) Representative H&E stained colonic sections. Scale bar, 100 μm. (F) Combined histopathology score in the colon. (G) Expression of Nos2, Kc and Tnfa in colonic RNA samples using qRT-PCR (fold-increases over mock-treated, mock-treated mice). (H) Bacterial numbers (CFU) recovered from colon contents. (C, D, G, H) Bars represent geometric means ± standard error. *, P < 0.05; **, P < 0.01; ns, not statistically significant (Student’s t-test). N is given in panels B and F.