lung microbiome

For a long time the lower lungs were thought to be sterile — clean, empty air sacs. We now know they host a small, low-density community of microbes called the lung microbiome. Think of it less as a crowded city like the gut and more as a sparse, ever-shifting frontier settlement.

This community is shaped by a balance of three forces: microbes drifting in from the mouth and inhaled air, microbes being cleared out by coughing and mucociliary action, and the local conditions of the airway. In health the populations are few and constantly turning over, dominated by ordinary mouth-associated bacteria rather than a stable resident flora.

The microbiome matters because its composition shifts in disease. In COPD, cystic fibrosis, bronchiectasis, and asthma, the balance tips toward fewer kinds of microbes and more potentially harmful species, and these changes can track with inflammation and flare-ups. The science is young, however, and much about cause versus consequence — and whether the lung microbiome can be deliberately reshaped for benefit — remains uncertain.