MUC5AC and cystic fibrosis: For instance, highly viscoelastic CF mucus, which is osmotically hyperconcentrated and rich in DNA and mucin, and associated with low mucociliary transport in CF lungs [6, 7], promotes robust biofilm formation by P. aeruginosa and other CF pathogens, including S. aureus, Haemophilus influenzae, Burkholderia cepacia complex (BCC), and C. albicans [8–11].