IBD patients can have reduced gut commensal abundance, relative expansion of pro-inflammatory taxa, and reduced microbial diversity and short-chain fatty acid production. FMT leads to clinical remission in some UC patients, but is a complex, nonscalable process with inconsistent composition/quality that has led to death from transmission of pathogens undetected in screening. VE202 is a rationally defined LBP of 16 beneficial Clostridia from clusters IV, XIVa, and XVIII, with properties including association with healthy human microbiomes, promotion of colonic Treg cells, production of beneficial and immunoregulatory metabolites, efficacy in mouse colitis models, and lack of overt pathogenic or toxigenic features.