Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Gram Staining { Created by Hans Christian Gram What is Gram Staining? Gram staining is a common experiment that is used to differentiate between two large groups of bacteria. The bacteria are differentiated by their cell wall components. The procedure distinguishes between two groups : Gram Positive and Gram Negative by staining them red or violet. Gram Positive bacteria have a thicker layer of peptidoglycan in their cell wall, so they stain violet because the substance retains the crystal violet stain. Gram negative bacteria have a thinner layer of peptidoglycan in their cell wall , so they stain red because they cannot retain the crystal violet stain. The Process! 1. Staining! Crystal Violet Dye The cells are stained with crystal violet dye. Next, Gram’s solution (iodine and potassium iodide) is added to form a larger molecule than the original crystal violet dye and iodine. This becomes insoluble in water. Gram’s Solution 2. Decolourising! Decolouriser A decolouriser such as ethanol alcohol or acetone is added to the sample. This shrinks and tightens the peptidoglycan layer. The crystal violet dye and Gram’s solution cannot penetrate the tightened peptidoglycan layer so instead it is trapped in the cell of the Gram Positive bacteria. On the other hand, the outer layer of the Gram negative bacteria has degraded and the thin peptidoglycan layer isn’t able to retain the dye or solution so the colour is lost. Gram Positive: Colour retained Gram Negative: colour lost 3. Counterstaining! Safranin A counterstain, often Safranin ( a weakly water soluble substance) is added to the sample, staining it red. Since Safranin is lighter than crystal violet, it doesn’t disrupt the colouration of Gram positive bacteria. The decolourised Gram negative cells are however stained red.