As a postdoctoral researcher, I expanded my study of bacterial byproducts into commensal gut microbial molecules. I observed that a bacterial metabolite, 4EPS, is almost 7-fold higher in plasma samples from children with ASD compared to controls. We identified novel biosynthetic genes from the gut microbiome for production of 4EPS and bioengineered gut bacteria to selectively produce it in mice. 4EPS was detected in the brain and was associated with changes in brain activity, myelination patterns, and anxiety-like behavior. This, along with my other preclinical work, has led to a clinical trial in close collaboration with Axial Therapeutics, where we report that an oral, GI-restricted adsorbent reduces circulating levels of 4EPS and other small phenolic molecules, and is associated with improvements in anxiety and irritability. These results suggest that targeting gut-derived metabolites is a safe approach to improving symptoms associated with ASD, thereby emboldening my future studies manipulating the levels of microbial metabolites for the modulation of host physiology and neurological symptoms.