Stain and Staining Procedures

Stain and staining procedures


Micro-organism can be identified by microscopic examination.These micro-organisms are very small, transparent, and invisible to our naked eyes so it is very difficult to observe these micro-organisms.

These microbial cells are colourless so when these cells are suspended in the aqueous medium the refractive index of the cell and aqueous medium is very low and same and due to lack of contrast observation of such unstained organism is very difficult. So staining of micro-organism in microbiology is an essential step for bacteriological studies.

Purpose of staining

  • Staining procedure helps in the production of contrast between micro-organism an aqueous medium.
  • It is useful to study morphological of bacteria.
  • Staining helps in studying internal as well as external characters of bacteria.


1. Dye – Dye is an organic compound made up of auxochrome and chromophore group these groups are linked to a benzene ring. Dye is used for colouring non-biological objects.

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