Negative stain

Definition

A negative stain is a staining technique used in microscopy where the background is stained, leaving the specimen unstained and visible against a dark background. This method helps to observe the morphology and size of microorganisms, including those that are difficult to stain.

5 Must Know Facts For Your Next Test

1. Negative stains use acidic dyes such as India ink or nigrosin.
2. The technique does not require heat-fixing, which preserves the natural shape of the microorganism.
3. Capsules of bacteria can be easily visualized using negative staining due to their resistance to most stains.
4. Negative staining is particularly useful for observing delicate structures like bacterial capsules and spirochetes.
5. The staining process involves mixing the dye with the specimen on a slide and then spreading it out to create a thin film.

Review Questions

Related terms

Simple Stain: A basic stain that colors all cells similarly, making them visible against a light background.

Gram Stain:

A differential stain that categorizes bacteria into Gram-positive or Gram-negative based on cell wall composition.

Acid-Fast Stain:

A differential stain used to identify acid-fast organisms like Mycobacterium species based on their waxy cell wall properties.