Mutations in the CFTR genes causing cystic fibrosis (CF) are associated with the presence of thick, viscous mucus and the formation of biofilms in the gastrointestinal tract (GI) that impair intestinal homeostasis, triggering chronic inflammation, epithelial barrier dysfunction, and changes in the composition and activity of the gut microbiota. This evidence concerns the gene CFTR and cystic fibrosis.