Gram Staining – How does it Work?
This video explains the principle behind Gram staining procedure. I have explained the difference between cell wall structure of Gram positive and Gram negative bacteria along with the function of each reagent.
It was given by Christian Gram in 1884 and it is also called differential staining because it differentiates bacterial in different groups – Gram positive and Gram negative, based on their cell wall structure.
00:15 introduction, 01:00 difference between Gram positive and Gram negative bacteria, 03:05 step by step protocol with function of each reagents.
Reagents used:
1.Crystal Violet – primary stain. It will stain both, Gram positive and Gram negative, bacteria.
2. Iodine – mordant. It makes a complex with crystal violet and forms CVI complex.
3. Alcohol – decolorizing agent. It washes off the CVI complex from the Gram negative bacterial cell wall.
4. Safranin – counter stain. It stains the colourless Gram negative bacteria.
Result: You will be able to observe Gram positive bacteria which would have taken up the primary stain and appears violet and Gram negative bacteria which would have taken up counter stain and appears pink/red in colour.
So let’s find out why some bacteria are Gram positive and some are Gram negative? 😊
Read more details on Staining mechanism here.
Similar to this, Acid fast staining is also a differential staining.