Comparison of the Morphology of Bacillus megatherium with Light and Electron Microscopy

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Abstract
Identical bacterial cells of B. megatherium were photographed first with the light microscope and later with the electron microscope in order to compare details of size, shape and structure as revealed by the two methods. The appearance of B. megatherium in electron micrographs is quite different from that of the same organism seen in light micrographs. Images in the electron micrographs indicate plainly the presence of 2 structures constituting the bacterial cell, an inner dense substance and an outer less dense substance. This outer substance of the bacterial cell is invisible in the light micrographs. This dissimilarity in appearance is the result not of difference in magnification but rather of the difference in light and electron optics. There is no significant difference between measurements of the size of unstained bacteria dried in air and photographed with the light microscope and measurements of the comparable portion (inner dense substance) of the identical bacteria later photographed in the electron microscope. Once the bacteria had dried in air their size remained unchanged in the chamber of the electron microscope. Measurements of the size of Bacillus megatherium obtained by Benians'' Congo-Red method were less than those of the total bacterial substance seen in the electron micrographs. This indicates that Benians'' method fails to outline the whole bacterial cell.