In this study, we have demonstrated that thick, viscous ASM+ containing mucin and extracellular DNA and incubated under static conditions with lowered oxygen tension (10% EO2) – constituents and conditions similar to those within the lung alveoli of CF patients – induces the formation of biofilm-like structures by P. aeruginosa and S. aureus, two of the pathogens most commonly seen in the infected lungs of these patients. Here, MUC5AC is linked to cystic fibrosis.