Difference Between Endotoxin and Enterotoxin

Key Difference – Endotoxin vs Enterotoxin
 

A toxin is a poisonous substance that is produced by a living cell or organism. Toxins are produced by different types of organisms such as bacteria, fungi, plants, and animals. Bacteria are well-known microorganisms which produce toxins that cause severe diseases such as tetanus, cholera, and diphtheria. Bacteria produce two types of toxins named endotoxins and exotoxins. Endotoxins are located within the bacterial cells. They serve as part of the bacterial cell wall and are made up of lipids. Endotoxins are released outside when the bacterial cell is lyzed. Exotoxins are poisonous proteins produced by bacteria. They are produced and released outside the bacterial cells. Enterotoxin is a type of exotoxin which is released to the intestine of organisms. These enterotoxins are produced by certain bacterial species and cause food poisoning and several intestine diseases. The key difference between endotoxin and enterotoxin is that endotoxin is a poisonous substance produced within the bacterial cell while enterotoxin is a poisonous substance which is produced in or released into intestines by bacterial cells.

CONTENTS

1. Overview and Key Difference
2. What is Endotoxin 
3. What is Enterotoxin
4. Similarities Between Endotoxin and Enterotoxin
5. Side by Side Comparison – Endotoxin vs Enterotoxin in Tabular Form
6. Summary

What is an Endotoxin?

Endotoxin is a poisonous substance present inside a bacterial cell that is released when the bacterial cell disintegrates. They are lipopolysaccharides which are located in the outer membrane of gram-negative bacteria. The outer membrane is unique to gram-negative bacteria. Hence, endotoxins are always associated with gram-negative bacteria. Some gram-negative bacterial species such as Escherichia coli, Salmonella, Shigella, Pseudomonas, Neisseria, Haemophilus influenza, Bordetella pertussis and Vibrio cholera are well-known endotoxin producers.

Endotoxin has three components in its structure: lipid A, O antigen (O polysaccharide) and polysaccharide. Toxicity is mainly associated with the lipid A component and antigenic nature is associated with O antigen. Endotoxins do not act enzymatically. They are also not normally soluble. However, endotoxins are heat stable and cannot be destroyed by boiling. Certain powerful oxidizing chemicals such as superoxide, peroxide, and hypochlorite can be applied to destroy endotoxins.

Figure 01: Endotoxins or Lipopolysaccharides in Gram-negative Bacteria

Endotoxins are not released to the outside till the cell is subjected to autolysis, external lysis or phagocytic digestion. They remain as a component of the outer membrane of the bacterial cell.

What is an Enterotoxin?

An enterotoxin is a protein exotoxin released by a microorganism that targets intestines. Enterotoxins are produced in or released into intestines. Certain bacterial species are capable of producing enterotoxins. Enterotoxins belong to the category of exotoxin. They are proteins and can act as enzymes. Enterotoxins are pore-forming toxins. Hence, they create pores in the epithelial cells of the intestine wall. When the enterotoxins increase the permeability to chloride ions in the intestinal mucosal cells, it causes secretory diarrhea. Staphylococcus aureus and E. coli are two bacterial species which can create such conditions by enterotoxins.

Figure 02: Action of Anthrax Exotoxins

In general, enterotoxins are produced by gram-positive bacteria. However, certain gram negative bacteria can also produce enterotoxins. For example, Vebrio cholera is a well-known enterotoxin producer and is a gram-negative bacterium.

What are the Similarities Between Endotoxin and Enterotoxin?

• Endotoxins and enterotoxins are produced by pathogenic bacteria.
• Endotoxins and enterotoxins are poisonous substances.

What is the Difference Between Endotoxin and Enterotoxin?

Summary – Endotoxins vs Enterotoxin

Endotoxins and enterotoxins are two types of poisonous substances produced by bacteria. Endotoxins are lipopolysaccharides and are components of the outer membrane of gram-negative bacteria. They are liberated when the bacterial cell disintegrates. Enterotoxins are a type of exotoxins that act on the intestine wall and cause diseases in the gastrointestinal tract. Endotoxins are lipids while enterotoxins are soluble proteins. This is the main difference between endotoxin and enterotoxin.

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References:

1.  Kenneth Todar Madison. “Bacterial Endotoxin .” Bacterial Endotoxin. N.p., n.d. Web. Available here 01 July 2017.
2. “Enterotoxin.” Wikipedia. Wikimedia Foundation, 05 June 2017. Web. Available here. 01 July 2017.
3. “Enterotoxin and Exotoxin.” World of Microbiology and Immunology. Encyclopedia.com, n.d. Web. Available here. 01 July 2017.

Image Courtesy:

1.” Gram negative cell wall” By Jeff Dahl – Own work (GFDL) via Commons Wikimedia
2. “Anthraxtoxins diagram en” By Y tambe – Y tambe’s file (CC BY-SA 3.0) via Commons Wikimedia

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