Figure 5. Propionate produced by Bacteroides spp. limits S. Typhimurium growth.

A) Fecal short chain fatty acid (SCFA) concentrations in uninfected B6N (red) and 129 (black) mice measured by gas chromatography-mass spectrometry (GC-MS). Data represent 2 independent experiments with 4–5 mice per group. Error bars represent the standard error of the mean. B) S. Typhimurium CFU/mL grown in medium supplemented with organic extracts of supernatants isolated from anaerobically grown Bt isolates. Extract concentration was normalized to Bt CFU/mL. Data represent 3 independent experiments with 4 replicates. Error bars represent the standard error of the mean. C-D, F) Anaerobic growth curves of S. Typhimurium in LB supplemented with propionic acid. C) OD600. D) Lag time. F) Maximal growth rate. Data represent 2 independent experiments with 3 replicates. Error bars represent the standard deviation. OD₆₀₀ was measured every 5 min for 24 h. E, G) Anaerobic growth curves of S. Typhimurium in LB broth supplemented with propionic acid or pH-matched LB broths. E) Lag time. G) Maximal growth rate. Data represent 2 independent experiments with 3 replicates. Error bars represent standard deviation. H-J) Time lapse imaging of anaerobic Salmonella grown on LB with and without propionate. H) Kymograph of representative single cells during growth. I) Time to the first cellular division. J) Maximal growth rate. Data represent at least 60 cells per condition. Error bars represent standard deviation. K-L) Anaerobic growth curves of S. Typhimurium in LB broth supplemented with propionic acid. K) Intracellular pH measurements over time. L) Intracellular pH measurement at maximal growth rate. Data represent 2 independent experiments with 3 replicates. Error bars represent standard deviation. For SCFA and commensal extract growth curves, significance was calculated using a two-tailed Mann-Whitney test; NS: not significant, *: p<0.05, **: p<0.01. For lag time, maximal growth rate, time to first division, and instantaneous elongation rate measurements, significance was calculated using an unpaired two-tailed t-test; *: p<0.05, **: p<0.01, ***: p<0.001, ****: p<0.0001. Unless noted, conditions are not significant.