FIGURE 6.

Schematic representation of the insights obtained from genomic analysis in context of tryptophan metabolism pathways in gut bacteria and their probable connection to brain. The six neuro-active compounds produced through bacterial tryptophan metabolism are depicted using various shapes as shown in the legend provided inside the figure. For each compound, the top three genera with respect to the “SCORBPEO” value are shown within rectangles having solid borders. For example, bacterial genera such as Klebsiella, Staphylococcus, Ralstonia, etc., produce indole acetic acid (IAA) in the large intestine through tryptophan metabolism. Probable ways by which each of the six compounds may alter the functioning of GBA (as collated from literature) have been indicated by yellow rectangles having dotted border. For instance, IAA may affect the interaction between gut and brain by acting as inter-cellular signaling molecule and immune system modulator. Apart from such mechanisms mediated by tryptophan metabolism products, sequestration of tryptophan by gut bacteria may have a direct impact on brain tryptophan level, which in turn can affect brain function.