During Gram staining, which compound is used as the counterstain?

During Gram staining, which compound is used as the counterstain?

• A. Crystal violet
• B. Iodine
• C. Safranin
• D. Alcohol

Answer: (C)

The counterstain in Gram staining is safranin. After the crystal violet-iodine complex is set and the alcohol decolorizer is applied, Gram-negative cells lose the primary stain and must be stained again to be visible. Safranin provides a distinct pink/red color to these decolorized cells, creating the contrast that allows you to differentiate them from the purple, Gram-positive bacteria. The other reagents have different roles: crystal violet is the initial stain that colors all cells; iodine acts as a mordant to fix that dye; alcohol decolorizes, removing the dye from Gram-negative cells.

The counterstain in Gram staining is safranin. After the crystal violet-iodine complex is set and the alcohol decolorizer is applied, Gram-negative cells lose the primary stain and must be stained again to be visible. Safranin provides a distinct pink/red color to these decolorized cells, creating the contrast that allows you to differentiate them from the purple, Gram-positive bacteria. The other reagents have different roles: crystal violet is the initial stain that colors all cells; iodine acts as a mordant to fix that dye; alcohol decolorizes, removing the dye from Gram-negative cells.