Studies with V. cholerae have shown that, to cause infection, cells need to swim through the intestinal lumen, traverse the mucus layer, and then colonize epithelial cells.32 The ability of V. cholerae to penetrate mucin is impaired in the presence of fecal and E. citroniae extracts, suggesting that small molecules present in these extracts may affect host colonization. The gene discussed is MUC5AC; the disease is infection.