In: Biology
What is Gram staining?
What is its significance?
What is the procedure of the Gram stain?
Answer 1:- Gram staining: It is a common staining techniques have proved very useful in taxonomic grouping of bacteria. Gram staining discovered by a Danish physician Christian Gram. The procedure involves staining the cells with crystal violet and then with iodine solution. The group of bacteria which retains the stain even after decolourization with alcohol is called Gram - postive, whereas those which lose stain after the treatment with alcohol are called Gram-negative. This differential reaction of two types of bacteria to crystal violet- iodine stain is due to different amount of lipids in their cell wall.
Answer2:- The Gram stain is the most important staining procedure in microbiology. It is used to differentiated between Gram -positive and Gram - negative bacteria .
Answer 3:- The Gram stain procedure includes following steps:
(1) Prepare a smear of the bacterium on the slide and stain it with the primary stain,crystal violet. All bacteria take purple stain of crystal violet.
(2) After 30 seconds rinse the slide with water and then put solution of potassium iodide and iodine( Gram 's iodine solution) on the slide. This solution serves as a mordant by complexing with the crystal violet as well as with the cellular material. All bacteria take a deep violet or purple stain.
(3) After 20 seconds rinse the slide with water. Now add drops of90% ethyl alcohol on the stained smear. This step is called decolorization.If the organism is Gram- negative, the dye complex used to stain the preparation is readily removed. However, if the organism is Gram- postive ,the dye is not entirely removed; as such the organism retains its purple colour.
(4) In the last step the slide is counter stained with safranin. Gram - negative organism, which become colourless when washed with alcohol, readily take the stain of safranin and appear red. Since the Gram- positive bacteria are already stained with the intense crystal violet dye,they remain purple in colour.
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