INTERNAL STRUCTURES OF A EUBACTERIUM SP. DEMONSTRATED BY THE NEGATIVE STAINING TECHNIQUE.

Bladen, Howard A. (National Institute of Dental Research, Bethesda, Md.), Marie U. Nylen, and Robert J. Fitzgerald. Internal structures of a Eubacterium sp. demonstrated by the negative staining technique. J. Bacteriol. 88:763-770. 1964.-Thin sections as well as negatively stained whole cells of a Eubacterium sp. isolated from the rat cecum were examined in a Siemens Elmiskop I electron microscope. The cell wall usually appeared in thin sections as a single dense layer about 130 A thick; however, occasionally it was demonstrated to be composed of three layers. The plasma membrane was approximately 130 A wide, and was composed of a denselight-dense arrangement. Intracytoplasmic membranous elements continuous with the plasma membrane were also observed in thin sections. When whole cells were negatively stained with phosphotungstic acid, the cell wall became transparent, and structures comparable in morphology to intracytoplasmic membranous elements were observed. These were demonstrated by stereomicroscopy to be in the interior environment of the cell, and appeared in many cases continuous with the cell wall. Frequently, they seemed to open to the exterior of the cell through what may be termed a pore. Small stalked structures similar to those described in mitochondria were observed along the periphery of the cell and occasionally along the walls of the internal elements.