Question

Identification of gram positive and gram negative by gram staining

Answer 1

TheGram-positive cell wall has a very thick peptidoglycan layer, which holds the crystal violet dye during the Gram staining procedure. The thick layer of peptidoglycan lies above the cell membrane

Gram-negative bacteria have a thinner layer of peptidoglycan (10% of the cell wall) and lose the crystal violet-iodine complex during decolorization with the alcohol rinse, but retain the counterstain Safranin, thus appearing reddish or pink.

Answer 2

Answer :-

The steps for the identification of Gram Positive (+ve) and Gram Negative (-ve) bacteria by gram staining method are as follows :-

• Any desired bacteria is chosen and is put on a slide.

• The bacteria on the first slide is then smeared by another slide.

• The smeared bacteria is then stained with Crystal Violet.

• The stained bacteria is then washed with water.

• After washing, the bacteria is stained with Iodine.

• The Iodine stained bacteria is then washed with either Absolute Alcohol or Acetone.

• After washing with Absolute Alcohol or Acetone, if the selected bacteria is Gram +ve in nature, then it will turn Purple and if the selected bacteria is Gram -ve in nature, then it will turn Pink.