Isolation and ultrastructure of Bacteroides sp. with external cell-wall layer (S-layer) in periapical osteitis.

Bacteroides sp. was isolated in human periapical osteitis and shown to be biochemically closely related to B. ruminicola ssp. brevis and B. capillus. Electron microscopic examination revealed an external cell-wall layer (S-layer). The fractionation of cells by various methods gave partially purified sheets corresponding to the observed layer with a hexagonal molecular arrangement.