Explain the function of the Gram stain’s decolorizer?

The function of the Gram stain’s decolorizer is crucial for differentiating between Gram-positive and Gram-negative bacteria. In this process, the decolorizer, usually alcohol or acetone, acts to remove the primary stain (crystal violet) from the cells. Gram-positive bacteria, which have a thick peptidoglycan layer in their cell walls, retain the crystal violet stain even after the application of the decolorizer. In contrast, Gram-negative bacteria, with their thinner peptidoglycan layer and an outer membrane, lose the crystal violet stain when the decolorizer is applied.

Consequently, after decolorization, Gram-negative bacteria can then absorb the counterstain (safranin), which gives them a pink appearance. This differential retention of the primary stain allows the Gram stain method to effectively categorize bacteria into these two groups based on their cell wall structure, which is fundamental in microbiology for identification and understanding bacterial characteristics.