Crystalline material showing square lattice arrays attached to the cell envelope of Corynebacterium diphtheriae grown in liquid cultures was demonstrated under the electron microscope using negative staining and sectioning techniques. Two types of lattice patterns could be found in the crystal. One was a square lattice consisting of parallel lines (about 3.2nm in diameter) with an average distance between their centers of 5.3nm. The second type of lattice pattern was composed of thinner parallel lines (approximately 2.2nm in diameter) with a closer periodicity being about 3.5nm. The two types of lattice patterns appeared to intersect each other at an angle of 45 degrees. The lattice arrays were disorganized and disappeared upon treatment with proteolytic enzymes, alkali and sodium dodecyl sulfate. This crystalline material seemed to be composed of protein(s) but not to be related to diphtheria toxin.
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