RICHARD-ALLAN SCIENTIFIC COMPANY 87101 Epredia

Gram Stain Kits – Tissue & Film Bacteria can be classified into one of two families based upon structural and compositional differences in their cell walls. Gram-positive bacteria have thick cell walls with high peptidoglycan content, whereas Gram-negative bacteria have thin cell walls with low peptidoglycan content. Both Gram-positive and Gram-negative bacteria stain with the dye- lake formed by Crystal Violet Solution and Gram’s Iodine Solution. However, during rinsing with Decolorizing Solution, this dye-lake is completely removed from the thin-walled Gram- negative bacteria, allowing them to be subsequently stained with Safranin O Stain Solution. The short duration of the decolorization step enables Gram-positive bacteria to retain the crystal violet dye-lake. Care should be taken when rinsing slides with Decolorizing Solution, as extended rinses can cause the crystal violet dye-lake to be removed from Gram-positive bacteria in addition to Gram-negative bacteria. Within the Tissue Kit only, tissue elements are then counterstained yellow by Tartrazine Stain Solution.