Differences Between Gram Positive And Gram Negative Bacteria

Gram Positive and Gram Negative bacteria are two major categories of bacteria distinguished based on their structural and staining characteristics. Below are the differences:

1. Cell Wall Composition

Gram Positive: The cell wall consists of a thick peptidoglycan layer.

Gram Negative: The cell wall is thin and composed of a lipopolysaccharide exterior layer.

2. Staining Reaction

Gram Positive: Retains the crystal violet dye and appears purple during Gram staining.

Gram Negative: Does not retain crystal violet dye and stains pink with a counterstain.

3. Antibiotic Sensitivity

Gram Positive: Susceptible to the enzyme lysozyme and antibiotics like penicillin.

Gram Negative: Resistant to penicillin due to the presence of an endotoxin called lipopolysaccharide.

4. Flagellar Structure

Gram Positive: The flagellum has two supporting rings located in the peptidoglycan layer and the plasma membrane.

Gram Negative: If present, the flagellum has four supporting rings: 'L,' 'P,' 'M,' and 'S' rings.

5. Presence of Teichoic Acids

Gram Positive: Teichoic acids are present, contributing to cell wall stability and rigidity.

Gram Negative: Teichoic acids are absent.

6. Lipoproteins

Gram Positive: Lipoproteins are absent.

Gram Negative: Lipoproteins are attached to the polysaccharide backbone, providing structural support.

Some of the differences of gram positive and gram negative bacteria are given in Table.

Sl. No.	Gram Positive	Gram Negative
1.	The cell wall is made up of a peptide glycan layer which is thick.	They have a thin lipopolysaccharide exterior cell wall.
2.	Effect on dyes: Retain the crystal violet dye, and change into purple during staining identification.	Effect on dyes: Do not retain the crystal violet dye, and react only with a counter-stain, generally stain pink.
3.	Effect on antibiotics: Susceptible to the enzyme lysozyme and to penicillin	Effect on antibiotics: Resistant to penicillin and contains an endotoxin called Lipopolysaccharide.
4.	The flagellum has two supporting rings, in the peptidoglycan layer, and in the plasma membrane.	If present, the flagellum has four supporting rings, namely the 'L' ring, 'P' ring, 'M' ring, and 'S' ring.
5.	Teichoic acids are present.	Teichoic acids are absent.
6.	Lipoproteins are absent.	Lipoproteins are attached to the polysaccharide backbone.
7.	Periplasmic space is absent.	Periplasmic space is present.