Using germ-free mouse models, researchers transplanted fecal bacteria from children on the autism spectrum and neurotypical children. Mice who received the transplants from the ASD cohort began to exhibit autism-like behaviors, whereas the mice who received transplants from typically developing children did not. Additionally, the mice showed altered gene expression in their brains and differences in types of metabolites present. In particular, the ASD mice had lower levels of 5AV and taurine. Findings suggest gut microbiota regulates autism-like behaviors via the production of neuroactive metabolites, providing further evidence for the gut-brain axis connection to the pathology of autism.