The goal of a new study was to explore whether fecal microbiota from human IBS patients with diarrhea has the ability to influence gut and brain function in recipient mice. Using fecal transplants, researchers transferred microbiota from IBS patients with or without anxiety into germ-free mice. The mice went on to develop changes both in intestinal function and behavior reminiscent of the donor IBS patients, compared to mice that were transplanted with microbiota from healthy individuals.