Ulcerative colitis (UC), an inflammatory bowel disease (IBD), is characterized by chronic inflammation of the colon, with severity of mucosal inflammation being associated with a higher risk of work disability, hospitalization, colorectal cancer, and colectomy. Non-specific immunosuppressive agents targeting the host, such as steroids, thiopurines, and/or biologics, are used to offset the natural history of disease in patients with moderate-severe inflammation. These therapies are, however, associated with significant risks and often ineffective in adequately managing disease. Genomic technologies have identified associations between microbial dysbiosis, or temporal shifts in composition, and UC severity. While recent efforts extended profiling of microbiota in UC beyond genomics, it remains poorly understood if these shifts are causal or associative in nature, and which mechanisms govern pathogenic roles of the microbiome in UC.