Figure 4. Inflammation generated nitrate required for propionate catabolism by S. Tm.

(A) Streptomycin-pretreated C57BL/6 mice were inoculated with an equal mixture of the indicated S. Tm strains. The competitive index in the colon content was determined 4 days after infection.

(B) Streptomycin-pretreated C57BL/6 mice were inoculated with WT S. Tm, ΔinvA ΔspiB, or mock treated. mRNA levels of Nos2 were measured in the cecal mucosa 4 days post-infection and normalized to β-actin mRNA levels.

(C–E) Streptomycin-pretreated C57BL/6 WT mice and Nos2-deficient mice were inoculated with an equal mixture of the WT S. Tm and ΔprpC mutant. One group was treated with aminoguanidine (AG) as indicated. (C) The competitive index in the cecal content was determined 4 days post-infection. (D) Nitrate concentration in the cecal and colonic mucus layer was determined by a modified Griess assay. (E) Combined histopathology score of pathological lesions in the cecum of mice from (C) (n = 5). (F) Propionate concentration in the cecal content of mice from (C) was determined by liquid chromatography/mass spectrometry (LC/MS) 2 days after infection.

(F and G) Streptomycin-pretreated C57BL/6 mice were inoculated with an equal mixture of WT S. Tm and ΔprpC in the indicated S. Tm strain backgrounds. The competitive index in the cecal content (F) and nitrate concentration in the cecal and colonic mucous layer (G) were determined 4 days post-infection. Each dot represents data from one animal (biological replicate). Bars represent mean ± SEM. *p < 0.05, **p < 0.01, ****p < 0.0001. See also Figure S4.