Intestinal mucus, encoded by Muc genes (up-regulated due to B. breve UCC2003 in this study), plays a crucial role in colonic protection via formation of a physical barrier between the gut lumen and IECs, and deficiencies in MUC-2 have been linked with experimental colitis and increased inflammation in patients with inflammatory bowel disease (Shirazi et al., 2000, Van der Sluis et al., 2006). Here, MUC2 is linked to colitis.