Crystal violet

Definition

Crystal violet is a purple dye used in microbiology for staining cells, particularly in the Gram staining procedure. It helps differentiate between Gram-positive and Gram-negative bacteria based on cell wall properties.

5 Must Know Facts For Your Next Test

1. Crystal violet is the primary stain in the Gram staining technique.
2. It binds to peptidoglycan layers in bacterial cell walls, making Gram-positive bacteria appear purple.
3. After crystal violet application, iodine is used as a mordant to form a crystal violet-iodine complex.
4. Gram-negative bacteria do not retain crystal violet after decolorization with alcohol or acetone due to their thinner peptidoglycan layer.
5. Crystal violet is also known as gentian violet and has antiseptic properties.

Review Questions

• What role does crystal violet play in the Gram staining procedure?
• Why do Gram-positive bacteria retain the crystal violet stain?
• How does crystal violet interact with bacterial cell walls?

Related terms

Gram Staining:

A differential staining technique that classifies bacteria into Gram-positive and Gram-negative.

Mordant:

A substance, such as iodine, used to set dyes on tissues by forming an insoluble compound.

Decolorizer: An agent like alcohol or acetone used in the Gram stain to remove crystal violet from certain types of cells.