Gram's fuchsin Solution

Gram's Fuchsin Solution is a reagent that could be used in qualitative procedures to differentiate gram-negative from gram-positive organisms. The Gram staining allows a fast differentiation of bacteria in Gram-positive and Gram-negative. The mureine structure of the bacteria walls is the basis of the color affinity. Bacteria will be stained with Gram's crystal violet solution - an aniline dye - in the first step. After the treatment with iod solution, a dye-iod complex will form. During the decolorizing step, this complex stays in the multilayer mureine structures of the Gram-positive bacteria and they will appear blue/violet. Gram-negative bacteria have a monolayer mureine structure only, the dye-iod complex does not stay bound to the cellwall, they will be decolorized. Gram-negative bacteria will be counterstained by Gram's Fuchsin solution and appear red/pink. Both Gram-positive bacteria and Gram-negative bacteria pick up the counterstain. The counterstain, however, is unseen on Gram-positive bacteria because of the darker crystal violet stain.