The ultrastructure of cultivable treponemes.

Cells of Treponema genitalis were studied in the electron microscope by means of negative staining and ultrathin sectioning techniques. All cells were covered by a regularly structured surface layer. This layer appeared to consist of pairs of thin fibrils attached to an amorphous layer. This amorphous layer in turn is probably identical with the exterior part of the outer membrane of the organism. The pairs of thin fibrils located on this surface were interconnected by polygons. The treponemes were regularly coiled and had somewhat tapered ends with 2-4 flagella inserted at each end. The two bundles of flagella were entwined around the cytoplasmic body of the cell and interdigitated in the middle region of the organism. Treatment of cells of T. genitalis with Myxobacter AL-1 protease 1, or with deoxycholate did not reveal intracytoplasmic tubules. This is in contrast to the results obtained with similar treatments of all other strains of species of Treponema hitherto examined.