Quarterly Journal of Microscopical Science, Vol s3-104, 145-153, Copyright © 1963 by Company of Biologists

A Note on the Fine Structure of a Spirochaete

¹ Department of Zoology, Downing St., Cambridge

A description is given, based on high-resolution electron micrographs of thin sections, of the structure of a spirochaete from the gut of a cockroach, Cryptocercus punctulatus. There is a central cell-body, the structure of which resembles that of a bacterium. Two kinds of granule are abundant in the cell-body: large ones, 150 to 250 A in diameter, of unknown composition, and small ones, identified as ribosomes, which may be arranged in whorls on the inner surface of the bounding membrane. Numerous small chromatin bodies are present. The bounding membrane of the cell-body is complex in structure. The cell-body is loosely enveloped by a sheath, made up of a thin membrane supporting a coarsely filamentous outer layer. In the space between sheath and cell-body is a loose bundle of 60 to 100 fibres. These are 140 A in diameter and are coiled helically around the cell-body. They resemble bacterial flagella and are thought to be responsible for the movements of the organism.