Electron Microscope Observations on the Behavior of the Bacterial Cytoplasmic Membrane During Cellular Division

Bacterial cells were fixed in OsO(4), washed, dehydrated, and embedded in a methacrylate mixture. Ultrathin sections were cut on a Porter-Blum ultramicrotome and were examined in an RCA electron microscope, type EMU-2D. The sections revealed that the cytoplasmic membrane undergoes a centripetal growth to form a membrane septum. This septum is formed as a double structure. Constriction of the daughter cells and deposition of cell wall material lead to the separation of the daughter cells. The bacterial cytoplasm appears to consist largely of 200 A granules and occasionally reveals arrays of parallel dense lines.