Why is the difference color between gram positive and gram negative bacteria?

Answer 1

It is because of the thickness of the peptidoglycan cell wall of the bacteria.

Gram positive bacteria have a larger/thicker cell wall.

It is this cell wall which retains the stain of the crystal violet(primary stain) and carbol fuschin(counterstain).

Gram negative have a very thin cell wall. So when the Acetone solution is applied in between stains the crystal violet is washed out of the gram negative bacteria. As it is only left on for a few seconds the gram positive bacteria can still retain the crystal violet solution due to the cell wall thickness.

The counterstain is then added. because the gram negative bacteria have been 'unstained' by the acetone the fuschin (pink stain) is absorbed and therefore shown when looked at under a microscope.

Answer 2

Gram positive bacteria appear blueish and Gram negative bacteria appear redish, after staining with Gram stain.

The reason why these bacteria react differently to gram staining procedure is because of differences in the structure of the cell wall between gram positive and negative organisms. Alcohol is used to counterstain the cell and gram positives retain the stain, whereas gram negative don't.

Answer 3

The cell wall of a bacterium is made up of short chain amino acids and sugars linked together called peptidoglycans. Depending on their thickness they will take up the grams stain. Gram+ve bacteria have a layer of peptidoglycans up to 5x thicker than Gram-ve bacteria. This layer retains the Crystal Violet/Iodine stain in Gram+ve bacteria whereas in Gram-ve it does no but they will take up the methyl red counterstain. Also Gram-ve bacteria have extra layers of lipo-polysaccharides and these also retain the counterstain.

Answer 4

Gram-positive bacteria have a thick mesh-like cell wall which is made up of peptidoglycan (50-90% of cell wall), which stains purple. Peptidoglycan is mainly a polysaccharide composed of two subunits called N-acetyl glucosamine and N-acetyl muramic acid. As adjacent layers of peptidoglycan are formed, they are cross linked by short chains of peptides by means of a transpeptidase enzyme, resulting in the shape and rigidity of the cell wall. The thick peptidoglycan layer of Gram-positive organisms allows these organisms to retain the crystal violet-iodine complex and stains the cells as purple

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 counter stain Safranin, thus appearing reddish or pink. They also have an additional outer membrane which contains lipids, which is separated from the cell wall by means of periplasmic space.

Answer 5

The difference in color between gram-positive and gram-negative bacteria is due to the structure of their cell walls. Gram-positive bacteria have a thick layer of peptidoglycan that retains the crystal violet stain, giving them a purple color. In contrast, gram-negative bacteria have a thin layer of peptidoglycan and an outer membrane that does not retain the stain, causing them to appear pink or red after counterstaining with safranin.

Answer 6

B'coz gm positive bacteria get stained with the colour of safranine...