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Monday, October 18, 2004

Special Topics in Gram Staining

Although the Gram-Stain process is outlined in a link below, this is an area describing the outcome of each step. (reference of Robert Bauman).

1) Flood the smear with Crystal Violet dye and then rinse with water. This primary stain colors all cells.
2) Flood the smear with Iodine solution for 1 min., then rinse with water. Iodine binds to a dye and makes it less soluble in water. All of the cells should be purple after this step.
3) Rinse with solution of ehanol and acetone for 30 sec., then rinse with water. This decolorizing agent breaks down thin cell walls that the Gram-negative cells have. These cells are now colorless, while the Gram-positive cells remain purple.
4) Flood the smear with safranin for 1 min. and then rinse with water. This red counterstain gives contrasting color to the primary stain. The slide is then blotted dry for microscopy. The thicker cell walls of the Gram-positives remain purple, while the Gram-negative cells are now pink.

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