EXTRACTION OF CRYSTAL VIOLET-IODINE COMPLEX FROM GRAM POSITIVE BACTERIA BY DIFFERENT SOLVENTS AND ITS IMPLICATION ON GRAM DIFFERENTIATION

Crystal violet from Gram stained S. aureus can be extracted completely by 95% ethanol if the stained bacteria is pre-treated with dilute sodium thiosulphate solution. Thiosulphate removes iodine form the cell component-dye-iodine complex instantaneously and renders the dye extractable by the differentiating medium. 1:1 alcoholic solutions of aniline, dimethyl aniline, nitro-benzene, benzene, toluene or xylol can also extract the color from the stained S. aureus; the extraction with the first three solvents is almost exhaustive while with the latter solvents extraction is appreciable but incomplete. These solvents can form charge-transfer complexes with iodine. The findings indicate that the stability of the cell component-dye-iodine complex determines the Gram-character of the cell. A model hasbeen presented for the Gram cell component-dye-iodine complex. © 1968 Springer-Verlag.