Explain the Gram Staining technique?

Gram staining is a differential staining procedure which divides bacteria into two groups: Gram positive and Gram negative, based on staining properties. The gram stain was developed in 1884 by the Danish Physician, Dr. Christian Gram. It is one of the most important and widely employed staining procedure in bacteriology.

It is very useful and is almost essential in identifying an unknown bacteria. The basis of gram staining is the difference in cell wall composition of two types of bacterial cells. Gram positives have thick cell wall, made up of multi-layered peptidoglycan with extensive cross-linking. On the other hand, gram negative cell wall has a very thin peptidoglycan layer surrounded by outer lipid rich outer membrane. There is no outer membrane in case of gram positives. This difference in cell wall leads to decolourization of gram negatives but not gram positives by decolourizing agent i.e., ethanol or acetone.