key term - Counterstain

Definition

A counterstain is a dye used in microscopy to provide contrast to the primary stain, allowing for better visualization of cellular components by staining structures that were not colored by the primary stain. It helps differentiate between different tissue types or microorganisms.

5 Must Know Facts For Your Next Test

1. Counterstains are typically used in differential staining techniques such as Gram staining and acid-fast staining.
2. Commonly used counterstains include safranin, methylene blue, and eosin.
3. In Gram staining, safranin serves as the counterstain to crystal violet, coloring Gram-negative bacteria pink or red.
4. The purpose of a counterstain is to provide a contrasting background that makes the primary stain more visible and easier to interpret under a microscope.
5. Counterstains can be essential for identifying cell morphology and distinguishing cellular components like nuclei from cytoplasm.

Review Questions

Related terms

Primary Stain: A dye that initially colors the specimen being observed under a microscope.

Differential Staining:

Techniques that use multiple stains to differentiate between different microorganisms or structures.

Gram Staining:

A differential staining technique that categorizes bacteria into Gram-positive and Gram-negative based on their cell wall properties.