Gram Differentiation Without the Use of Iodine

Abstract

A difference in the decolorization of the two types of cells is essential for Gram differentiation; Gram-positive cells being less decolorizable than Gram-negative cells. In practice, if a high molecular weight alcohol or aniline is used, a successful differentiation of both cells can be made by Gram procedures without iodine. Iodine plays a secondary role in that by its application, all cells are made less decolorizable than they would be without iodine. The formation of a dye-iodine precipitate within the cells seems to be the best explanation of the experimental findings.