What is the difference between positive gram and negative gram?

Answer 1

The major difference between gram positive and the gram negative bacteria is the structure of their cell wall. The gram positive bacteria have two layers a plasma membrane and outer to it a peptidoglycan layer. But the gram negative bacteria have another layer other than the cell wall. While the gram negative bacteria has three layers. It has a plasma membrane that is called as the inner membrane, then a peptidoglycan layer and finally an outer membrane of phospholipids and lipopolysaccharides. There is space between the inner membrane and the peptidoglycan layer called as the periplasmic space.

Peptidoclycan layer in the gram positive bacteria are much more thicker than that of the gram negative bacteria.

The molecule teichoic acid is present in gram positive bacteria and the porin proteins are characteristically present in the gram negative bacteria.

Gram positive bacteria usually produce exotoxins and the gram negative bacteria usually produces endotoxins.

Gram positive bacteria gives Violet colour to the gram staining and the gram negative bacteria gives pink colour to the gram staining. In gram staining the bacteria is fixed on slides and then they are treated with Crystal Violet. After that they are treated with iodine and then they are decolourised. If the bacteria is gram negative then it shows Violet colour and if it is gram negative then it shows pink colour. Initially both strains show Violet colour after Crystal Violet treatment but on the treatment with iodine and decolourisation the gram negative bacteria loose colour and become pink. This is because in the gram positive bacteria the Violet crystals bind firmly to the peptidoglycan layer and the colour is not removed in later stages. In gram positive bacteria the colour does not penetrate much because of outer membrane and is lost much during decolourisation.

Answer 2

Positive gram staining indicates that the bacteria retain the crystal violet dye and appear purple under the microscope, while negative gram staining indicates that the bacteria do not retain the dye and appear pink or red. This difference is due to variations in the bacterial cell wall structure, with positive gram bacteria having a thick peptidoglycan layer and negative gram bacteria having a thinner peptidoglycan layer.