Difference Between Endotoxins and Exotoxins

Microbes can be found practically anywhere, both within and outside of living beings. Toxins produced by these microorganisms are the primary cause of illnesses. Toxins are classified into two types:

  • Endotoxins
  • Exotoxins

The primary distinction between endotoxins and exotoxins is how bacteria generate these toxins. Let’s take a closer look at the distinction between endotoxins and exotoxins.

Differences between Exotoxins and Endotoxins

What Is Exotoxins?

Exotoxin is a type of secretory protein found in Gram-positive and Gram-negative bacteria. It can harm host cells by interfering with their normal metabolism or by directly destroying them. As a result, they are extremely poisonous and immunogenic. Furthermore, their symptoms are fatal. Exotoxins include botulinum toxin, which is generated by Clostridium botulinum, diphtheria toxin, which is produced by Corynebacterium diphtheriae, and tetanospasmin, which is produced by Clostridium tetani. Furthermore, all three poisons are neurotoxins.

What Is Endotoxins?

Endotoxins are a sort of toxic substance that spreads into the surrounding medium, causing significant damage to the host by interfering with normal cell activity.

They are also heat stable liable proteins that form a structural component of the gram-negative bacteria’s cell wall. They are only released upon cell lysis or bacterial death.

Endotoxins are abundant in Vibrio cholerae, Neisseria gonorrhoeae, E. coli, Pseudomonas, Salmonella, Haemophilus influenzae, and Shigella.

Key Differences Between Exotoxins and Endotoxins

  • Exotoxins are secreted by live cells, whereas endotoxins are a component of the cell wall.
  • Exotoxins can be found in both gram-positive and gram-negative bacteria, whereas endotoxins can only be found in gram-negative bacteria.
  • Endotoxins are complex lipopolysaccharides, whereas exotoxins are basic polypeptides.
  • Exotoxins are relatively heat vulnerable at 60 degrees Celsius and thus extremely unstable, whereas endotoxins are heat tolerant even at 100 degrees Celsius.
  • Endotoxins have a low immunity, whereas exotoxins have a high antigenicity.
  • Exotoxins produce toxoid, which is employed in formalin treatment, but endotoxins do not produce toxoid.
  • Exotoxins are extremely poisonous and lethal, whereas endotoxins are moderately toxic and lethal.
  • Exotoxins generally bind to specific receptors, whereas endotoxins do not bind to specific receptors.
  • Exotoxins are found on extrachromosomal genes, whereas endotoxins are found on chromosomal genes.
  • Exotoxins are denatured when subjected to high boiling temperatures, whereas endotoxins are not denatured even after exposure.
  • Exotoxins produce diseases such as tetanus, diphtheria, and botulism, whereas endotoxins induce diseases such as meningococcemia and gram-negative rod sepsis.
  • Endotoxin causes fever in the host, but exotoxin does not.
  • There are effective vaccinations for exotoxins, but there are none for endotoxins.
  • Exotoxins are extremely toxic even in minute amounts, whereas endotoxins are extremely lethal in huge numbers.
  • Exotoxins enter host cells through particular receptors, whereas endotoxins do not.
  • Exotoxin has a high affinity for certain tissues, whereas endotoxin has no affinity for specific tissues.
  • Exotoxin has a molecular weight of 10KDa, whereas endotoxin has a molecular weight of 50-1000KDa.
  • Exotoxins can be filtered, whereas endotoxins cannot.
  • Exotoxin is capable of eliciting immunological responses, but endotoxin is incapable of eliciting immune responses.
  • Exotoxin is active beyond 60 degrees Celsius, whereas endotoxin is active beyond 100 degrees Celsius.

Similarities between Exotoxins and Endotoxins

  • Bacteria are responsible for both.
  • Both infect the host with illnesses.
  • Both are found on the chromosomes.
  • Both are poisonous.
  • Heat can have an effect on both.


Endotoxin is a lipopolysaccharide found on pathogenic bacteria’s outer membrane. They are heat stable yet mildly immunogenic and moderately poisonous. They are also pyrogenic. Meanwhile, enterotoxins are exotoxins that induce food poisoning and diarrhea in the intestine. They are also heat resistant. Exotoxins are proteins that harmful bacteria emit into their environment. They are also extremely antigenic and poisonous. As a result, they can cause potentially fatal illnesses such as tetanus, diphtheria, and botulism. The primary distinction between endotoxin, enterotoxin, and exotoxin is their incidence, immunogenicity, and toxicity.