During Gram staining, what is the function of the crystal violet?

Crystal violet functions as the primary stain in the Gram staining process, which is an essential differential staining technique used in microbiology. When a sample is subjected to Gram staining, crystal violet is applied first and penetrates bacterial cell walls, leading to the coloration of cells. This staining is crucial because it allows for the subsequent differentiation between Gram-positive and Gram-negative bacteria based on their cell wall structure.

In Gram-positive bacteria, which have thick peptidoglycan layers, the crystal violet binds strongly and retains the purple color even after the decolorization step. In contrast, Gram-negative bacteria, which have a thinner peptidoglycan layer and an outer membrane, will lose the crystal violet during the decolorization step but will later take up the counterstain (safranin) for visualization. The primary role of crystal violet is foundational in identifying bacterial characteristics during the Gram staining process.