| Crystal violet is a basic triphenylmethane dye. Crystal violet staining solution is commonly used in Gram staining to distinguish between Gram-positive and Gram-negative bacteria. Crystal violet can bind to the peptidoglycan in bacterial cell walls, forming a colored complex. Because Gram-positive bacteria have a thicker cell wall with a high peptidoglycan content, the crystal violet-iodine complex is difficult to wash out with ethanol, so they appear purple. In contrast, Gram-negative bacteria have thinner cell walls with less peptidoglycan, allowing the crystal violet to be removed by ethanol, after counterstaining, they appear red. In addition, crystal violet can bind to nucleic acids and acidic substances within cells to form a purple complex, thereby staining cells for visualization of colony numbers. This makes it useful in cytological experiments for assessing cell proliferation or migration activity. |
