The purpose of a mordant in the Gram stain is to:a. remove the simple stain. b. make gram-negative cells visible. c. prevent the crystal violet from leaving the cells. d. make the bacterial cells larger. e. make the flagella visible.
Gram staining is a staining techniques used for the identification of bacteria in microbiological studies.
Gram staining uses crystal violet as the primary stain. It complexes with the peptidoglycan cell wall of Gram positive bacteria giving them a purple color.
An iodine mordant is also used that forms a crystal violet-iodine complex that fixes the crystal violet dye to the cell wall. This prevents the Gram positive cell walls from being decolorized by the application of alcohol.
A counter stain, safranin is then applied that stains Gram negative bacteria pink.
