Fig 4. Salmonella requires the gut microbiota to benefit from 1,2-propanediol-utilization.

(A-B) Germ-free Swiss Webster mice or ex germ-free mice pre-colonized with either B. thetaiotaomicron (B. theta) or B. fragilis for 7 days were infected intragastrically with a 1:1 mixture of S. Typhimurium wild type and a pduA-X mutant. Bars represent geometric means ± s.e.m. of the competitive index (CI) recovered from colon contents (A) or cecal contents (B). N is indicated in panel C. (C) Histopathological changes were scored for sections of the cecum. (D) Representative images of histological sections from the cecum. Scale bar represents 100 μm. m, mucosa; s, submucosa; ml, muscularis. (E) Germ-free Swiss Webster mice or ex germ-free mice mono-associated with B. thetaiotaomicron for 7 days (N = 6) were infected intragastrically with the indicated S. Typhimurium strains and the 1,2-propanediol concentration was determined 3 days later. Bars represent geometric means ± s.e.m.; LOQ, limit of quantification. (F) Medium containing the sugars indicated at the top was inoculated with the S. Typhimurium strains indicated on the right. Sugar fermentation was detected through the color change (blue to yellow) of a pH indicator. (G) A pduC mutant or a fucO mutant was grown anaerobically in minimal medium containing fucose as a sole carbon source. The spent culture medium was supplemented with tetrathionate and inoculated with the indicated mixture of S. Typhimurium strains to determine the CI after anaerobic growth. (H) Germ-free mice (N = 4) were mono-associated with B. thetaiotaomicron and inoculated with the indicated strain mixtures. (G and H) Bars represent geometric means ± s.e.m. of the competitive index (CI).