Fig. 2.

The diversity of indole-containing compounds in serum is affected by the microbiome. (Upper) Various indole-containing molecules arise only in the presence of the microbiome and ultimately enter the plasma by means of different routes. (Lower) Differences in the plasma levels of indole-containing compounds attributed to the action of the microbiome. The integrated signal intensities plotted on the y axes are reduced by a factor of 1,000.