Abstract
Listgarten, M. A. (Harvard School of Dental Medicine and Forsyth Dental Infirmary, Boston, Mass.), W. J. Loesche, and S. S. Socransky. Morphology of Treponema microdentium as revealed by electron microscopy of ultrathin sections. J. Bacteriol. 85:932-939. 1963.-Broth cultures of a strain of Treponema microdentium were harvested on Millipore filters, fixed in osmic acid, and sectioned for electron microscopy. The sections revealed that the spirochetes had an axial filament, made up of two fibrils approximately 150 A in diameter, which was situated between an external envelope approximately 140 A in thickness and a protoplasmic cylinder. The protoplasmic cylinder had a cross-sectional diameter of 100 to 200 mmu, and was surrounded by a double "membrane" consisting of two 40-A electron-dense structures separated by a 45-A space. Cross-sections of spirochetal "granules" revealed that the limiting membrane was continuous with the outer envelope of the spirochetes, and surrounded the protoplasmic cylinder and axial filament.