Until recently, the mucus layer of our lungs has remained unexplored. Many respiratory diseases such as asthma, chronic obstructive pulmonary disease (COPD) and cystic fibrosis are characterized by an excessive accumulation of thick mucus. Afflicted people suffer repeated lung infections and breathing difficulties caused by clogged airways, resulting in severely reduced quality of life. We address this issue by developing an unprecedented probiotic approach that self-regulates mucus thickness to protect and promote respiratory health. Our engineered bacteria sense the pathologically altered osmotic pressure caused by thickened mucus, thus triggering the expression of mucus degrading enzymes. For a proof-of-concept we degrade mucus, envisioning to clear the airways and consequentially remove entrapped pathogens and harmful particles. As pioneers in the field of lung probiotics, we challenge conventional treatments by exploring the lung microbiome as a potential solution to manage mucus-related respiratory diseases.