Difference Between Gram Positive and Gram Negative Cell Wall

The key difference between gram positive and gram negative cell wall is that the gram positive cell wall has a thick peptidoglycan layer with teichoic acids while gram negative cell wall has a thin peptidoglycan layer surrounded by an outer membrane. Another major difference between gram positive and gram negative cell wall is that the gram positive cell wall stains in purple colour in grams staining while grams negative cell wall stains in pink colour.

Bacteria are tiny microorganisms with a single cell. They have a cell wall surrounding their cell membrane. Features of the cell wall are highly useful when differentiating bacteria. Grams’ staining is a technique which categorizes bacteria into two major groups: gram negative bacteria and gram positive bacteria.

CONTENTS

1. Overview and Key Difference
2. What is the Characteristic of Gram Positive Cell Wall
3. What is the Characteristic of Gram Negative Cell Wall
4. Similarities Between Gram Positive and Gram Negative Cell Wall
5. Side by Side Comparison – Gram Positive vs Gram Negative Cell Wall in Tabular Form
6. Summary

What is the Characteristic of Gram Positive Cell Wall?

Grams positive bacteria are a category of bacteria. Their cell wall is known as gram positive cell wall. This is because it has a thick peptidoglycan layer. It is multilayered and possesses teichoic acids. In grams staining, gram positive cell wall stains in purple colour due to the retention of crystal violet stain.

Gram positive cell wall has a low lipid concentration and a low lipopolysaccharide concentration. It also does not possess an outer membrane. Hence, most gram positive bacteria are susceptible to antibiotics. They also do not have a periplasmic space.

What is the Characteristic of Gram Negative Cell Wall?

Gram negative bacteria have a cell wall which has a thin peptidoglycan layer. It only has a single layer. However, gram negative cell wall has an outer membrane surrounding the peptidoglycan layer. This outer membrane has porins, lipopolysaccharides, and lipids. Hence, it provides antibiotic resistance to bacteria. Furthermore, it has a large periplasmic space.

When grams staining is performed, gram negative cell wall stains in pink colour. Thickness of the cell wall is 8-12 nm. Unlike gram positive bacterial cell wall, gram negative bacterial cell wall does not contain teichoic acids. But it has a high concentration of lipids.

What are the Similarities Between Gram Positive and Gram Negative Cell Wall?

• Gram positive and negative cell walls are present in bacteria.
• Both contain peptidoglycan layer.
• They provide structural support to bacteria.

What is the Difference Between Gram Positive and Gram Negative Cell Wall?

The thickness of the peptidoglycan layer is the main difference between gram positive and gram negative cell wall. The cell wall of gram positive bacteria has a thick peptidoglycan layer (20-30 nm) while cell wall of gram negative bacteria has a thin peptidoglycan layer (8-12 nm). The former is multilayered while the latter has only a single peptidoglycan layer. Hence, they stain in different colours during the grams staining technique. Grams positive cell wall stains in purple colour while grams negative cell wall stains in pink colour. Gems negative bacteria are antibiotic resistant than gram positive bacteria. This is because gram negative cell wall is impermeable and has an outer membrane.

Moreover, gram positive cell wall does not contain an outer membrane while gram negative cell wall does. Also, the former is less resistant to antibiotics whereas the latter is more resistant to antibiotics. There are Teichoic acids in the gram positive cell wall, but not in the gram negative cell wall. Moreover, the lipopolysaccharide and lipid concentrations in gram positive cell wall are lower than in gram negative cell wall.

Summary – Gram Positive vs Gram Negative Cell Wall

It is this cell wall in bacteria that helps to differentiate bacteria. The basic difference between gram positive cell wall and gram negative cell wall is the thickness of the peptidoglycan layer.

Reference:

1. Salton, Milton R.J. “Structure.” Medical Microbiology. 4th Edition., U.S. National Library of Medicine, 1 Jan. 1996, Available here.

Image Courtesy:

1. “Figure 22 02 08f” By CNX OpenStax – (CC BY 4.0) via Commons Wikimedia
2. “Gram negative cell wall” By Jeff Dahl – Own work (CC BY-SA 4.0) via Commons Wikimedia