The mucolytic bacterium R. gnavus, closely associated with the high-risk cluster C.3, has already been linked to IBD in multiple studies.8,35,36 Interestingly, R. gnavus may correlate with active inflammation,36 as histological inflammation is strongly associated with colorectal cancer risk in IBD.37 While alterations were less clear in C.2, Alistipes, which has been associated with sporadic colorectal cancer38 as well as mediating colitis-associated cancer risk in Lipocalin-2-deficient/Il10-deficient mice,39 was enriched in this cluster (Figure 6a). Here, LCN2 is linked to inflammatory bowel disease.