The human airway has two aqueous layers that are vital for normal lung function. A mucous layer traps inhaled bacteria and foreign particles. A thin layer of airway surface fluid (ASL) lines the epithelial surface, providing a microenvironment that enables cilia to clear mucus from the airway. Cystic fibrosis (CF) is a disease associated in part with impaired mucociliary clearance, abnormally thick mucus, chronic infections, and inflammation in the lung. The lungs of healthy individuals are free from bacterial infection, whereas the lungs of CF patients are chronically infected by bacteria such as Staphylococcus aureus and Pseudomonas aeruginosa, which can destroy the lungs (reviewed by