Difference Between Endotoxins And Exotoxins

There are many microbes found almost everywhere around us, both inside and on the surfaces of the human body. These pathogens produce toxins which are the major causes of the various infectious diseases. These toxins are categorized into two types:


They are heat stable proteins or lipopolysaccharide, consisting of a lipid and a polysaccharide that form primary structural components of the gram-negative bacterial cell wall. These toxins are liberated on the cell’s Lysis. Endotoxins are pyrogens; which are fever causing agents.

Endotoxin, as the name suggests, it is the toxin that is liberated from the outer cell wall of a bacteria after its death. These toxins are extremely dangerous to the extent that they can cause severe damage to the organism.


They are heat-labile proteins, mainly secreted by some rare species of bacteria. Once after the toxins are liberated, it diffuses into the surrounding medium and causes harm to the host cells either by disrupting the normal functioning of the cell or by directly destroying the cells. Exotoxins, as the name suggests, are the toxin produced inside the bacteria itself as a part of their metabolism.

The basic difference between Endotoxins and Exotoxins lies in the way how these toxins are produced by bacteria.

Difference Between Endotoxins And Exotoxins

These toxins widely vary in toxicity and lethality. But Exotoxins are much more potent and often fatal when compared to endotoxins. The deadliest toxin in the world – Botulinum toxin or Botox is produced by the bacterium Clostridium botulinum.

The other major difference between Endotoxins and Exotoxins are summarized below:

Endotoxin Exotoxins
The toxin forms a part of the cell wall and is released upon the death of the bacteria  The toxin is excreted as a part of metabolism
Toxins are composed of a Lipoglycan complex The toxin is composed of polypeptides
It has the ability to trigger an immune response is comparatively weaker
It has the ability to trigger an immune response
It does not have any enzymatic activity.
Most of the activities are enzymatic in nature.
Moderate toxicity It is highly toxic.
Cannot be more into toxoids
Extremely toxic and often fatal in larger quantities
Cannot be more into toxoids
Can be made into a Toxoid
Does not get denatured Gets denatured on boiling
Examples of endotoxin-producing bacteria are:

  • Salmonella typhi (Typhoid),
  • Vibrio cholerae (Cholera).
  • Streptococcus pneumoniae (sepsis )
Examples of exotoxin producing bacteria are:

  • Clostridium botulinum (Botox),
  • Clostridium tetani (Tetanus),
  • Corynebacterium diphtheriae (Diphtheria).
Diseases caused by these toxins include:

  • Urinary tract infections
  • Coronary artery disease
  • Meningococcal meningitis.
Diseases caused by these toxins include:

  • Scarlet fever
  • Botulism
  • Scalded skin syndrome.

Learn more about Endotoxins, Exotoxins, their differences and other related topics @ BYJU’S Biology

Leave a Comment

Your email address will not be published. Required fields are marked *