Positive stain

Definition

A positive stain is a technique in microscopy where the dye binds directly to the specimen, making it stand out against a lighter background. This type of staining enhances the visibility and contrast of the microorganisms or cellular structures being observed.

5 Must Know Facts For Your Next Test

1. Common dyes used in positive staining include crystal violet, methylene blue, and safranin.
2. Positive stains work by binding to negatively charged molecules on the surface of cells.
3. Gram staining is a well-known example that utilizes positive staining techniques.
4. Positive stains are used primarily to highlight specific features such as cell walls, spores, or nuclei.
5. The process typically involves fixing the specimen to ensure that it adheres properly to the slide before applying the dye.

Review Questions

Related terms

Negative Stain: A technique where the dye does not bind to the specimen but instead stains the background.

Gram Stain:

A differential staining method that classifies bacteria into Gram-positive or Gram-negative based on their cell wall composition.

Fixation:

The process of preserving and adhering a specimen to a microscope slide before staining.