Distal colon of a healthy wild-type mouse

Distal colon of a healthy wild-type mouse, universal Eub338 Cy3 probe, x400. Bacteria (orange fluorescence) are clearly separated from the colonic wall by a mucus layer. Bacterial concentrations within the colon are high. Water from the fecal stream softens the mucus layer, and mature mucus is carried away by the fecal stream. The mucus layer is continuously rebuilt, resulting in onion-like stratification on the border between stool and the mucus layer (arrows).