The Structure of Mycoplasma pneumoniae as Determined by the Freeze‐Substitution Technique

The ultrastructure of Mycoplasma pneumoniae FH was examined by a mild fixation method, the freeze‐substitution technique, for thin‐section transmission electron microscopy and the following new findings were obtained. In the cytoplasm, no nuclear region could be clearly identified. The cytoplasm was filled with many ribosome‐like particles, fine fibers and electron‐dense particles. The electron‐dense particles appeared to be similar to the particles found in the nucleoid region of Pseudomonas aeruginosa and might therefore possibly be a kind of DNA binding protein. The cell surface was completely enveloped with a thin opaque layer. The presence of this surface layer prevented any direct contact of the cell surface with that of the two M. pneumoniae cells.