Although the tested mucin/mucus concentrations are lower than the reported ones in healthy airway mucus and CF sputum,18, 19 the observed phenomenon corroborates the biochemical effects of mucus, which inhibits cell‐to‐cell communication and, as recently reported by Wheeler et al., also influences the biofilm formation.17 On the contrary, when decreasing mucin or mucus concentrations, which corresponds to an increase of the ratio between bacteria population to mucin or mucus amount (i.e., the setting of infection), the pyocyanin production was not inhibited, yet significantly promoted. The gene discussed is MUC5AC; the disease is cystic fibrosis.