Ultrastructural identification of spirochetes and flagellated microbes at the brush border of the large intestinal epithelium of the rhesus monkey.

Spiral-shaped organisms exclusively and intimately populate the brush border of the cecal and colonic epithelium of healthy monkeys (Macaca mulatta). These organisms replace the glycocalyx, destroy most microvilli, and attenuate the terminal web of the brush border. Despite these remarkable alterations, the remaining host cellular structure is unchanged. Two structurally distinct microbes, a spirochete and a flagellate, were recognized by electron microscopy. These spirochetes share the general characteristics of other known spirochetes: they are 3 to 6 mum long and 0.2 to 0.4 mum wide, spiral 2 to 6 times, and have axial fibrils of 6-12-6 and 4-8-4 arrangements. Flagellated microbes are 4 to 6 mum long and 0.2 to 0.4 mum wide, spiral 2 to 4 times, and are characterized by a polar flagellum which originates from the terminal button at each end of the cytoplasmic body. This in vivo ultrastructural study of anaerobic spiral-shaped organisms bypasses the difficulties of in vitro culture techniques and provides a detailed description and identification of these organisms in their host environment.