What is a Gram's stain technique?

This method has been invented by a Danish bacteriologist named Hans Christian Gram and involves the staining of bacteria with special coloured compounds to understand their cell wall composition. First, the cells are stained with a purple dye (Crystal Violet) for 30secs, after this step, the cells are flooded with Gram’s Iodine for another 30secs which forms a large dye complex with the purple dye and bind to the thick peptidoglycan layer of Gram positive bacteria. Then, the stained cells are decolourised with alcohol which tightens the peptidoglycan layer by dehydrating it, thus preventing the purple-iodine dye complex from escaping the layer but decolourising the very thin peptidoglycan layer of the Gram negative bacteria. In the final step of the experiment, Safranin is introduced for 30 more seconds staining it red and because of the light weight of the substance it does not affect the heavy colouring of the Gram positive cells, nevertheless colouring the Gram negative cells red.

The Gram stain technique is a method used to differentiate bacterial species into two groups based on the structure of their cell walls. It was developed by the Danish bacteriologist Hans Christian Gram in 1884. The technique involves staining bacterial cells with crystal violet dye, followed by iodine treatment, alcohol wash, and counterstaining with safranin. Gram-positive bacteria retain the crystal violet dye and appear purple under a microscope, while Gram-negative bacteria lose the dye and appear pink or red after counterstaining.