To test these hypotheses, P. aeruginosa was evolved in synthetic cystic fibrosis media (SCFM) in the presence (+mucin) or absence (−mucin) of mucin in the absence of co-occurring species ([None]) or in two pairwise (S. maltophilia [SM] or S. aureus [SA]) and one three-species ([SM + SA]) community for ~130 generations (Fig. S1). This evidence concerns the gene MUC5AC and cystic fibrosis.