Ultrastructure of the Surface of <i>Rickettsia prowazeki</i> and <i>Rickettsia akari</i>

Abstract

Negative-contrast electron microscopy revealed that the outer layer of the envelope of rickettsiae is composed of a matrix of tetragonally arranged subunits. The layer projects approximately 7 nm from the cell wall. It is suggested that this outer layer is analogous to the structure considered capsule-like in morphology.