Nigrosin

Definition

Nigrosin is a negatively charged, acidic dye used primarily in negative staining techniques. It provides a dark background that contrasts with the lighter, unstained cells.

5 Must Know Facts For Your Next Test

1. Nigrosin is commonly used to stain bacterial capsules because it does not penetrate the cell wall.
2. The dye creates a stark contrast between the background and the transparent organisms, enhancing visibility under a microscope.
3. Since nigrosin is an acidic dye, it has a strong affinity for positively charged cellular components.
4. Negative staining with nigrosin helps to preserve the morphology and size of microorganisms better than positive staining methods.
5. It is particularly useful in identifying shape and arrangement of bacteria that are difficult to stain with other methods.

Review Questions

Related terms

Negative Staining: A technique where the background is stained instead of the organism, making the cells appear clear against a dark background.

Capsule Staining: A differential staining method used to detect bacterial capsules by utilizing dyes like nigrosin or India ink.

Acidic Dye: A type of dye that carries a negative charge and binds to positively charged cell structures.