Extended Data Fig. 4: Supplementation with glucose or pectin inhibits indole production by repressing tnaA gene expression.
(a) Indole production measured in the culture supernatants of E. coli, B. theta and C. sporogenes cultured individually in either LB broth or LB broth supplemented with 0.5 % glucose or 1 % glucose. Bars and error lines show mean ± SD of two independent biological replicates. (b) Indole production measured in the culture supernatants of defined communities consisting of E. coli (E), B. theta (B), P. anaerobius (P) and C. spo (C) cultured in either mGAM or mGAM supplemented with 0.5 % pectin. Bars and error lines show mean ± SD of two independent biological replicates. (c) Defined community consists of E. coli, B. theta and C. spo are cultured together in mGAM medium supplemented with either 0.02 or 0.05 % free tryptophan and with or without 0.5 % apple pectin. Total RNA was extracted after 24 hrs fermentation and mRNA levels were measured as described in methods and reported as relative difference (fold change) to the 0.02% Trp condition. Bars and error lines show mean ± SEM of three independent biological replicates. Metabolites data are shown in Fig. 3. Relative expression from RT-qPCR to measure tnaA mRNA levels in E. coli and in B. theta in response to pectin supplemented (0.5%) in the growth medium after 24 hrs fermentation at either low (0.02%) or high tryptophan (0.05%) concentrations is shown here. Unpaired two-tailed t-tests were performed on the expression ratios to determine the statistical significance of the relative expression differences. P values are shown in the figure panels.
