What is the function of safranin in the Gram staining procedure?

Safranin serves as a counterstain in the Gram staining procedure, which is crucial for identifying Gram-negative bacteria. During the staining process, cells are first stained with crystal violet (the primary stain), and then subjected to a decolorization step, typically using alcohol or acetone. This decolorization step removes the crystal violet from Gram-negative cells, which have a thinner peptidoglycan layer. Safranin is then applied, which stains these decolorized Gram-negative cells pink.

The differential staining with safranin allows for the clear identification of Gram-positive cells (which retain the crystal violet and remain purple) and Gram-negative cells (which take up the safranin and appear pink). This distinction is critical in microbiology as it provides important information about the cell wall properties of the bacteria, informing further testing and treatment options.

Thus, safranin’s role as a counterstain is essential for visualizing and differentiating between the two groups of bacteria following the decolorization step.