Capsule Staining Technique by Maneval’s Method.

Capsule Staining Technique by Maneval’s Method.

Maneval’s  staining method is a negative staining method.

Aim

To stain a  capsule of a cell by Maneval’s staining method.

Requirement

  1. 1 % Congo red solution.
  2. Maneval’s stain.
  3. Capsulated cell culture.

Procedure

  1. Take a loopful of capsulated cell suspension on a clean grease free slide.
  2. Add a drop of 1 % congo red solution in the suspension and then spread it gently on the slide to form a smear.
  3. Allow the suspension to air dry and do not heat fix it.
  4. Flood the slid with Maneval’s stain and keep it for 2 minutes.
  5. After 2 minutes discard excess stain and do not water wash the slide.
  6. Allow the slide to air dry and observe under oil immersion objective.

Flow chart of Capsule staining by Maneval’s method

Flow chart of Capsule staining by Maneval's method
Flow chart of Capsule staining by Maneval’s method

Mechanism

  • As we know capsules are non-ionic in nature so they do not get stain easily.
  • By using the negative staining method  demonstration of capsule becomes easy.
  • So in this method first we use congo red stain as it is acidic stain it stain the background in red colour.
  • Further we use Maneval’s stain this stain has four important components and they are-
  1. 10 % FeCl3 – It acts as chemical fixative.
  2. 5 % phenol – It increases penetration power of stain.
  3. Acid fuchsin – It is a basic dye it stains the cell.
  4. Acetic acid – It decreases the pH of smear to acidic side.
  • Due to acetic acid pH is shifted to acidic side and due to which congo red stain turns red to blue in colour that is why the colour of background changes from red to blue in colour.
  • Due to acid fuchsin the cell get stained in pink colour.
  • It creates a clear contrast in between cell, capsule and background and due to which capsule can be detected easily.

Note

Congo red stain is a indicator dye at acidic pH it appears blue in colour while at neutral pH it appears red in colour.

Observation

We can observe pink colour bacterial cell at the center surrounded by colourless capsule against dark blue colour background.

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