Inflammatory bowel diseases involve chronic inflammation of digestive tract tissues. Chronic gut inflammation is often caused by uncontrolled immune responses triggered by an imbalanced gut microbiome. To study inflammatory bowel diseases, fecal microbes from patients are often directly transferred to experimental mice, but the microbiome–inflammation relationship and how the gut environment shapes microbiome composition are still not well understood. A consistent animal model is needed to clarify the cause-effect relationship between gut inflammation and microbiome imbalance. So, researchers transplanted mice with and without gut inflammation either directly with human fecal microbes or indirectly with stool from the mice treated with human fecal microbes (mouse-adapted microbes). Mice treated with human fecal microbes had variable colitis symptoms, while those given the mouse-adapted microbes had more consistent symptoms. Gut inflammation affected the microbiome composition in mice after transplant, and inflamed mice had an unhealthy microbiome that caused more severe colitis. The findings imply that inflammation promotes growth of aggressive microbes, driving microbiome imbalance and triggering further inflammation This mouse model may help in studying disease characteristics related to human microbiome transfer and could be generalized to models of other diseases linked to human microbiota.