Inflammatory bowel disease (IBD) is less common in parts of the world with parasitic worm infections than in the developed world. Understanding why may lead to new types of therapy. We recently found that infection by parasitic worms increases the number of beneficial anti-inflammatory Clostridiales bacteria in the intestine, and that these bacteria can outcompete harmful disease-causing bacteria. Therefore, one reason why people living in the developed world are more likely to develop IBD may be because their intestines are no longer colonized by these beneficial bacteria. To restore a healthy “gut microbiome”, we may need to recolonize patients with these beneficial bacteria as a way to treat IBD. We propose to isolate beneficial Clostridiales bacteria from indigenous people of Malaysia who are infected by parasitic worms. These bacteria are potentially more beneficial when administered to IBD patients. We will test this by examining their ability to kill harmful disease-causing bacteria and restore a healthy gut microbiome. We will also use an animal model of IBD to determine whether this approach can reverse disease. If successful, we believe that Clostridiales from indigenous Malaysians, or products that these bacteria produce, can be used to treat IBD.