Fig. 6: Metabolite–microbe associations.
a, Venn diagram showing the overlap of 128 measured metabolites classified as host- or microorganism-related, based on PICRUSt2 predictions of microbial metabolic functions and the mouse metabolic network. The majority of metabolites cannot be classified as either host- or microbe-associated, seven metabolites are host-related and thirteen metabolites are microorganism-related. Twenty-seven metabolites did not match any of the metabolic networks. b, Distribution of the correlation coefficients of 126,336 metabolite–microbe pairs. Zoomed-in bars show how applying thresholds on the P value, the SPF–germ-free fold change and the presence of metabolic enzymes reduces the number of predicted functional metabolite–microbe pairs to 148. c, Sankey diagram showing links between unique metabolites and the corresponding microbial orders in positively correlated metabolite–microbe pairs that meet the thresholds defined in b. Metabolites are colour-coded according to MetaCyc. The size of the linkage line denotes number of pairs. d, Spatial profiles of metabolite concentrations and associated microorganisms in SPF lumen samples. Lines with a shaded area indicate the mean ± s.e.m. of concentration measurements with five male mice, and the mean ± s.e.m. of relative microorganism abundance. Abbreviations: duo, duodenum; jej, jejunum; ile, ileum; cec, cecum and col, colon.
