What dye is used in a capsule stain?

A positive capsule stain requires a mordant that precipitates the capsule. By counterstaining with dyes like crystal violet or methylene blue, bacterial cell wall takes up the dye. Capsules appear colourless with stained cells against dark background.

What kind of stain would be used to see a capsule?

Bacterial capsules are non-ionic, so neither acidic nor basic stains will adhere to their surfaces. Therefore, the best way to visualize them is to stain the background using an acidic stain and to stain the cell itself using a basic stain. We use India ink and Gram crystal violet.

What stains use acidic dyes?

Histological Stains other than H&E

Acidic dyes
Acid fuschin	Red
Aniline Blue	Blue
Eosin	Red
Orange G	Orange

What is not stained in a capsule stain?

Bacterial capsules are composed of high-molecular-weight polysaccharides and/or polypeptides, and are associated with virulence and biofilm formation. Unfortunately, capsules do not stain well with crystal violet, methylene blue, or other simple stains.

Why don’t you heat fix a capsule stain?

Most bacterial capsules are composed of polysaccharide however some genera produce polypeptide capsules. Capsular material is very moist (slimy) and any heating will cause it to shrink – it is for this reason that we will not heat fix the slide before staining.

What two things are stained in a capsule stain?

In this method, two dyes, crystal violet, and India ink are used. The capsule is seen as a clear halo around the microorganism against the black background. This method is used for demonstrating Cryptococcus. The background will be dark (color of India ink).

Is an example of acidic stain?

Acidic Dyes: It is dye which has negative charge so they bind to positively charged cell structures like some proteins. Acidic dyes are not very often used in Microbiology lab. except to provide background staining like Capsule staining. Examples: Nigrosine, Picric acid, Eosin, Acid fuschin, India ink etc.

What is the charge of an acidic dye?

Acidic dyes have a net negative charge and bind to components of cells and tissues that are positively charged. Ionized amino groups in proteins (side chains of lysine and arginine).

What happens if you heat fix a capsule stain?

THE CAPSULE STAIN – The Gin Stain Most bacterial capsules are composed of polysaccharide however some genera produce polypeptide capsules. Capsular material is very moist (slimy) and any heating will cause it to shrink – it is for this reason that we will not heat fix the slide before staining.

What kind of dye is used to stain capsules?

By counterstaining with dyes like crystal violet or methylene blue, bacterial cell wall takes up the dye. Capsules appear colourless with stained cells against dark background. Capsules are fragile and can be diminished, desiccated, distorted, or destroyed by heating.

What is the principle of capsule staining in chemistry?

The principle of capsule staining is based on staining of background with an acidic stain and staining of bacterial cell with a basic stain. A capsule being non-ionic will not stain by either of the two dyes. Thus, capsule staining creates contrast by staining a bacterial cell along with its background and leaving a capsule as a colourless halo.

Which is the best stain for bacterial capsules?

Bacterial capsules are non-ionic, so neither acidic nor basic stains will adhere to their surfaces. Therefore, the best way to visualize them is to stain the background using an acidic stain (e.g., Nigrosine, congo red) and to stain the cell itself using a basic stain (e.g.,crystal violet, safranin, basic fuchsin and methylene blue).

Can a positive capsule stain be obtained from India ink?

India ink is difﬁcult to obtain nowadays; however, nigrosin is easily acquired. A positive capsule stain requires a mordant that precipitates the capsule. By counterstaining with dyes like crystal violet or methylene blue, bacterial cell wall takes up the dye. Capsules appear colourless with stained cells against dark background.