ELECTRON MICROSCOPY OF THE FINE STRUCTURE OF CORYNEBACTERIUM DIPHTHERIAE, WITH SPECIAL REFERENCE TO THE INTRACYTOPLASMIC MEMBRANE SYSTEM

Abstract

Cells of Coryne bacterium diphtheriae, grown in glucose-yeast extract-broth enriched with bovine serum under aerobic conditions, were fixed with osmium tetroxide in acetate-veronal buffer containing NaCl and CaCl2, followed by uranyl acetate treatment and embedding in methacrylates. The fine structure of the organism was observed on the sections with an electron microscope.
The cell wall is composed of three layers; dense outer and inner layers and the less-dense broad intermediate layer. The cytoplasmic membrane consists of a double layered membrane, i.e., dense inner and outer layers separated by a lighter interspace. At the process of cell division the cell wall associated with the cytoplasmic membrane grows centripetally to form the septum. The nuclear apparatus consists of the fine fibrils, about 20∼50 A width, in a low density matrix occupying the central area of the cytoplasm.
The cytoplasmic membrane enters the cytoplasm and appears to be reorganized into the intracytoplasmic membrane system, which is presented as a complex membranous organnelle, such as a cluster of vesicules and a lamellar structure, inside as well as outside the nuclear region. The organelle often can be seen on the inner rim of the developing septum. As the cell grows older, the membranous organelle seems to degenerate, while the metachromatic granules appear in the cytoplasm and gradually develop with age.