When do you use Indian ink stain?
Microbiologists use India ink to stain a slide containing micro-organisms. The background is stained while the organisms remain clear. This is called a negative stain. India ink, along with other stains, can be used to determine if a cell has a gelatinous capsule.
What is the general principle involved in capsular staining?
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 is the principle behind negative staining?
6.1. Negative staining is based upon the principle that there is no reaction between the stain and the specimen. This is accomplished when the stain is used at a pH at which the interaction between stain and biological materials is negligible.
Which stain solution is also called as Indian Ink?
Negative-staining with nigrosin or India ink is a quick and easy method to gain information about the presence or absence of capsules or any other layers around bacteria.
Why is India ink used for negative staining?
India Ink or Nigrosin is an acidic stain. This means that the stain readily gives up a hydrogen ion (proton) and the chromophore of the dye becomes negatively charged. Since the surface of most bacterial cells is negatively charged, the cell surface repels the stain.
Why is it called India Ink?
Black ink was known as masi in India: a mixture of different ashes, water and animal glue. It was only in the mid-17th century, when Europe began importing ink from India, that it became known as Indian ink.
What is India ink method?
India Ink Preparation is a test to detect the presence of Cryptococcus neoformans, a type of encapsulated yeast that is capable of surviving in both animals and plants. It is usually found in soil that is extremely contaminated with bird droppings.
How is India ink used in negative staining?
In negative staining method, an acidic dye is used known as India Ink or Nigrosin. When the bacterial cells are exposed to this stain, due to the presence of acidic nature it readily gives up a hydrogen ion (proton) and the chromophore. As a result, the dye becomes negatively charged, now the bacterial cell surface deflects the stain.
How is the principle of negative staining used?
Principle of Negative Staining. Negative staining requires the use of an acidic stain such as India ink or nigrosin. The acidic stain, with its negatively charged chromogen, will not penetrate the cells because of the negative charge on the surface of bacteria. Therefore, the unstained cells are easily discernible against the colored background.
Which is an acidic dye in India ink?
India Ink or Nigrosin is an acidic stain. This means that the stain readily gives up a hydrogen ion (proton) and the chromophore of the dye becomes negatively charged. Since the surface of most bacterial cells is negatively charged, the cell surface repels the stain.
How do you make a capsule stain with India ink?
Place a single drop of India ink on a clean microscope slide, adjacent to the frosted edge. Using a flamed loop and sterile technique, remove some Klebsiella pneumoniae from culture tube or plate and mix it into the drop of India ink.