The abundance of Ruminococcaceae_UCG-014 was found to be positive correlated with the expression levels of intestinal barrier indicators, including MUC2, Occludin, claudin-1, etc., in Ulcerative colitis (UC).48 Cao et al. also demonstrated that Ruminiclostridium UCG-014 was negatively correlated with the gut barrier damage in mice.49 For Parasutterella, though there is no direct evidence about its effect on intestinal barrier, it has been reported to be associated with intestinal inflammation, including irritable bowel syndrome, intestinal chronic inflammation and Crohn’s disease. Here, CLDN1 is linked to Crohn disease.