Exotoxins

Exotoxin are protein or polypeptide. It acts on tissues away from the starting point of bacterial growth. Exotoxins are usually produced by bacteria or cellular action. It is released into the environment by bacteria.

Exotoxins are normally formed during bacterial cell growth. The production of toxins is characteristic of certain strains of disease-causing bacteria. For example, Corynebacterium diphtheria is responsible for producing diphtheria toxin and Clostridium tetani are responsible for producing tetanus toxin. These are virulent bacterial strains responsible for toxin production, whereas non-toxic strains are not responsible for such products at all. Exotoxins are considered the most dangerous and toxic substances.

Also Read: Gram Staining

Exotoxin Function

The exotoxins have following functions:

• Exotoxins target specific cells or tissues in the host organism.
• They can interfere with essential cellular processes, such as protein synthesis or cell signaling.
• Exotoxins may disrupt the host’s immune system, allowing the bacteria to evade detection and clearance.
• Some exotoxins can cause tissue damage or organ dysfunction, leading to symptoms of infection.
• Certain exotoxins have enzymatic activity, which can further contribute to their harmful effects on the host.

Types of Exotoxins

Exotoxins come in three primary categories:

• Superantigens (Type I toxins)
• Exotoxins (Type II toxins) that harm host cell membranes
• A-B toxins, and other toxins that impair host cell function (Type III toxins)

Why Exotoxins are Harmful?

• A toxin produced by bacteria is known as an exotoxin.
• An exotoxin can harm the host by killing cells or preventing normal cellular metabolism. 
• They are extremely powerful and capable of causing the host considerable harm. 
• Like endotoxins, exotoxins can release themselves or leak during cell lysis.

Exotoxin Example

Some examples exotoxins:

• Tetanospasmin (produced by Clostridium tetani, causing tetanus)
• Botulinum toxin (produced by Clostridium botulinum, causing botulism)
• Diphtheria toxin (produced by Corynebacterium diphtheriae, causing diphtheria)
• Cholera toxin (produced by Vibrio cholerae, causing cholera)

The major difference between endotoxin and exotoxin lies in how bacteria produce these toxins. Endotoxins are produced by Gram-negative bacteria and exotoxins are produced by bacteria that release toxins into the surroundings. The toxins are toxic substances, including proteins, small molecules, and peptides, which cause disease upon contact with or absorption from body tissues.

The difference between endotoxin and exotoxin lies in their origins and how they affect the body. In this article, we will cover the difference between endotoxin and exotoxin in tabular form.