Fig. 5

ILA promotes the microbial production of IPA and IAA in vitro. The colonic microbiota was cultured under anaerobic conditions with or without an addition of de Man Rogosa Sharpe (MRS) medium, cell-free supernatant (CFS) of L. reuteri I5007, or ILA for 12 h at 37 °C. A The concentrations of IPA and IAA in the anaerobic culture supernatant of the colonic microbiota (n = 4). B PCoA plot of the Bray–Curtis distance among different treatment groups (n = 4). C Relative abundance of three major enzymes involved in microbial tryptophan metabolism as predicted by PICRUSt2. D Network analysis of differentially enriched bacterial genera and enzymes. Edges representing significant Spearman’s correlations indicate |r|> 0.7 and p < 0.05. The thickness of each line is proportional to the magnitude of the correlation. The pie chart shows the relative abundance (%) of bacterial genera or enzymes among different groups. ArAT, aromatic amino acid aminotransferase; ID, indolepyruvate decarboxylases. Relative abundances of acyl-CoA dehydrogenase (ACD) (E) and indoleacetamide hydrolase (IAAH) (F) predicted by PICRUSt2 among DSS-treated mice administered with or without ILA (see the Figure S7 legend for experimental details). G The C. sporogenes was cultured with or without an addition of Tryptophan, L. reuteri I5007, ArAT-deficient mutant L. reuteri I5007(△L.R), CFS of L. reuteri I5007 or △L.R, ILA for 24 h at 37 °C (n = 4). *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001; ns, not significant