New Preparation Techniques for the Electron Microscopy of Bacteria

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Abstract
Techniques are described whereby aerobic bacteria can be studied by means of the electron microscope with a minimum of disturbance. The techniques involve the formation of a collodion membrane 100 to 200 A thick on the upper surface of a solid or liquid nutrient medium and the inoculation of the upper side of this membrane with a dilute suspension of the organisms to be studied. When the organisms have grown sufficiently as observed by light-microscope examination, the membrane supporting the growth is removed, mounted on a wire screen, dried, and inserted in the electron microscope. If grown under sufficiently dry conditions, the physical relationships between the cells and other products of growth appear to be preserved in the mounted specimens. The specimens prepared by these techniques were singularly free of obscuring background material and desiccation artifacts. The techniques have proved uniformly successful in the prepn. of specimens of Bacillus mycoides, B. megatherium, and Escherichia coli grown under a number of different conditions and subsequently treated in several different ways.