What substance is used as a decolorizer in the Gram staining process?

In the Gram staining process, ethanol is the substance used as a decolorizer. This step is crucial for distinguishing between Gram-positive and Gram-negative bacteria. During the staining procedure, Gram-positive bacteria retain the crystal violet dye due to their thick peptidoglycan cell wall and do not lose color when washed with ethanol. In contrast, Gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane, which allows the ethanol to penetrate and wash away the initial dye, leading to a color change.

The choice of ethanol as the decolorizer is particularly effective because it alters the permeability of the bacterial cell wall. This property allows it to selectively decolorize Gram-negative cells while preserving the color of Gram-positive cells. Understanding the role of ethanol in the Gram stain is fundamental to microbiology, as it helps in the identification and classification of bacteria based on their cell wall characteristics.