The nasal mutualist AMBR11 supports homeostasis via multiple mechanisms.

Comparing the nasal microbiome of healthy individuals and chronic rhinosinusitis (CRS) patients revealed as a species clearly associated with nasal health, although isolates obtained from healthy individuals are scarce. In this study, we explored the properties of this understudied lactic acid bacterium by integrating comparative genomics, habitat mining, cultivation, and functional characterization of interaction capacities. Mining 10.000 samples from the Earth Microbiome Project of 17 habitat types revealed that is mainly associated with the human nasal cavity. AMBR11 isolated from the nose of a healthy individual exerted antimicrobial activity against , decreased proinflammatory cytokine production in airway epithelial cells, and larvae mortality induced by this important nasal pathobiont. Furthermore, the strain protected the nasal barrier function in a mouse model using interleukin-4 as disruptive cytokine. Hence, AMBR11 is a mutualist with high potential as topical live biotherapeutic product.