In a broader context, the presence of oral anaerobes in other, mucus-rich disease environments where both oral anaerobes and P. aeruginosa are major players–chronic obstructive pulmonary disease, sinusitis, and ventilator-associated pneumonias–suggests that mucin fermentation and metabolic cross-feeding may be a more widespread phenomenon. This evidence concerns the gene MUC5AC and chronic obstructive pulmonary disease.