Bacterial biofilms contribute to CRC, e.g., carcinogenic subtypes pks+ E. coli and enterotoxigenic Bacteroides fragilis cooperatively induce tumors in co-colonized mice. The reduction of the mucus layer by ETBF allowed pks+ E. coli to come into close proximity with the intestinal epithelium [99,100,101]. This evidence concerns the gene ARAF and colorectal carcinoma.