Structural studies of the surface projections of Chlamydia trachomatis by electron microscopy.

Rod-like projections on the surface of Chlamydia trachomatis have been studied by a combination of computer image analysis and electron microscopy. The rods, c. 60-80 A in diameter and c. 500 A in length, were found on the surface of prokaryocells of C. trachomatis inserted in the cytoplasmic membrane through a ring-like structure in the outer membrane. The rod-like structures were found at all stages of the life cycle, even in very small elementary bodies (EBs) of C. trachomatis and in vesicles < 0.2 micron. Computer image analysis of isolated rods indicated that they comprise helically arranged subunits with a periodicity of c. 50 A. From their localisation and distribution, these structures may be related to the proliferation, or to the infectivity, of chlamydiae.