Difference between exotoxins and endotoxins


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Exotoxins vs Endotoxins
Many bacteria produce toxins, enzymes and pigments. Toxins and enzymes play important role in pathogenecity. Toxins mainly are of two types:

Exotoxins are usually heat labile proteins secreted by certain species of bacteria which diffuse into the surrounding medium.
Endotoxins are heat stable lipopolysaccharide-protein complexes which form structural components of cell wall of Gram Negative Bacteria and liberated only on cell lysis or death of bacteria.

Exotoxins verus Endotoxins

  1. Excreted by organisms, living cell
  2. Found in both Gram positive and Gram Negative bacteria
  3. It is polypeptide
  4. Relatively unstable, heat labile (60°C)
  5. Highly antigenic
  6. Toxoids can be made by treating with formalin
  7. Highly toxic, fatal in µg quantities
  8. Usually binds to specific receptors
  9. Not pyrogenic usually, Toxin Specific
  10. Located on extrachromosomal genes (e.g. plasmids)
  11. Filterable
  12. It has no enzymatic activity
  13. Its molecular weight is 10KDa
  14. On boiling it gets denatured.
  15. Detected by many tests (neutralization, precipitation, etc)
  16. Examples: Toxins produced byStaphylococcus aureus, Bacillus cereus, Streptococcus pyogenes, Bacillus anthrcis(Alpha-toxin, also known as alpha-hemolysin (Hla))
  17. Diseases: Tetanus, diphtheria, botulism

  1. Integral part of cell wall
  2. Found mostly in Gram Negative Bacteria
  3. It is lipopolysaccharide complex.
  4. Relatively stable, heat tolerant
  5. Weakly immunogenic
  6. Toxoids cannot be made
  7. Moderately toxic
  8. Specific receptors not found
  9. Fever by induction of interleukin 1 (IL-1) production, Shock
  10. Located on chromosomal genes
  11. Not Filterable
  12. It has mostly enzymatic activity
  13. Its molecular weight is 50-1000KDa
  14. On boiling it can not be denatured.
  15. Detected by Limulus lysate assay
  16. Examples: Toxins produced by E.coli, Salmonella Typhi, Shigella, Vibrio cholera(Cholera toxin- also known as choleragen)
  17. Diseases: Meningococcemia, sepsis by gram negative rods