Demonstration of mucosa-associated microbial populations in the colons of mice.

Gram-stained sections prepared in a microtome-cryostat and examined by light microscopy confirmed the observation with scanning electron microscopy made by other workers that microbes inhabit a zone adjacent to the mucosal surface of the proximal colon of mice. Microbes in the midcolon, in contrast, are restricted to the fecal pellets occupying the intestinal lumen.