Capsule staining

Definition

Capsule staining is a differential staining technique used to visualize the polysaccharide capsules that surround certain bacteria. It involves staining the background and the bacteria, but leaving the capsule itself unstained, resulting in a clear halo around the bacterial cells.

5 Must Know Facts For Your Next Test

1. Capsule staining helps differentiate between encapsulated and non-encapsulated bacterial cells.
2. Common dyes used in capsule staining include India ink or nigrosin for the background and crystal violet or safranin for the cells.
3. The capsule appears as a clear, unstained area surrounding the stained bacterial cell because it does not take up most stains.
4. Capsules are important virulence factors that help bacteria evade phagocytosis by host immune cells.
5. Streptococcus pneumoniae, Klebsiella pneumoniae, and Haemophilus influenzae are examples of bacteria with prominent capsules that can be visualized using capsule staining.

Review Questions

Related terms

Gram Staining:

A differential stain that classifies bacteria into gram-positive and gram-negative based on cell wall composition.

Endospore Staining: A special stain used to detect endospores within bacterial cells by applying malachite green followed by safranin.

Acid-Fast Staining:

A differential stain used primarily to identify Mycobacterium species based on their waxy cell walls that retain carbol fuchsin dye.