FN1 and colorectal carcinoma: At the species level, in the control group, unclassified_Muribaculaceae, unclassified_Prevotellaceae_NK3B31_group, unclassified_Prevotellaceae_UCG_001, and unclassified_Clostridia_UCG_014 were significantly more abundant than the CRC, CRC + Fn and CRC + Fn + Cys groups.