Differences Between Exotoxins and Endotoxins 4.63/5 (664)

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Differences Between Exotoxins and Endotoxins

Many bacteria produce toxins, enzymes and pigments. Toxins and enzymes play important role in pathogenecity. Toxins 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.

Differences Between Exotoxins and Endotoxins

Some of the differences between Exotoxins and Endotoxins are as follows:





Excreted by organisms, living cellIntegral part of cell wall


Found in both Gram positive and Gram Negative bacteriaFound mostly in Gram Negative Bacteria


It is polypeptideIt is lipopolysaccharide complex.


Relatively unstable, heat labile (60°C)Relatively stable, heat tolerant


Highly antigenicWeakly immunogenic


Toxoids can be madeby treating with formalinToxoids cannot be made


Highly toxic, fatal in µg quantitiesModerately toxic


Usually binds to specific receptorsSpecific receptors not found


Not pyrogenic usually, Toxin SpecificFever by induction of interleukin 1 (IL-1) production, Shock


Located on extrachromosomal genes (e.g. plasmids)Located on chromosomal genes


FilterableNot so


It has no enzymatic activityIt has mostly enzymatic activity


Its molecular weight is 10KDaIts molecular weight is 50-1000KDa


On boiling it get denatured.On boiling it cannot be denatured.


Detected by many tests (neutralization, precipitation, etc)Detected by Limulus lysate assay


Examples: Toxins produced by Staphylococcus aureus, Bacillus cereus, Streptococcus pyogenes, Bacillus anthrcis(Alpha-toxin, also known as alpha-hemolysin (Hla))Examples: Toxins produced by E.coli, Salmonella Typhi, Shigella, Vibrio cholera(Cholera toxin- also known as choleragen)


Diseases: Tetanus, diphtheria, botulismDiseases: Meningococcemia, sepsis by gram negative rods
Differences Between Exotoxins and Endotoxins

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Differences Between Exotoxins and Endotoxins

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The Author

Sagar Aryal

Sagar Aryal

I am Sagar Aryal, a passionate Microbiologist and the Scientific Blogger. I did my Master's Degree in Medical Microbiology and currently working as a Teaching Assistant at St. Xavier's College, Kathmandu, Nepal. I am particularly interested in research related to Medical Microbiology and Virology. Find me on Facebook, Twitter or Linkedin !!!


Add a Comment
  1. World workers (researchers, scientists, academics) need to integrate within new discoveries for!

    Mondskalaj gelaboristoj necesas interliĝi pri novaj serĉadoj

  2. want to join microbiology society

  3. its is inspiring and excellent too

  4. thanks for nice notes

  5. Thanks sir it enriching.

  6. what is the difference between pyrogen testing and endotoxin testing?

  7. Sir it is good
    My question is why endotoxines not converted to toxoids?

    1. because endotoxine gram +Ve and -Ve and exotoxine just gram -Ve

  8. thanks a lot sir

  9. Thnku for this valuable notes

  10. Important informations..great thanks

  11. very nice thanks

  12. I am a master student of microbiology. I wonder if anyone could help me find the answers of the two questions below:
    1-Are there any bacterial toxins that are not secreted out and are kept within the cell?
    2-Are there any lipid toxins?

    1. 1st :endotoxins are not secreted out of the cell , they only act when lysis of bacteria occurs.
      2nd : endo toxins are lipid toxins , they are structural component of bacterial cell wall , in form of lipopolysachride

  13. I am a microbiologist am very much interested in medical microbiology. Very good and nice post sir keep it up!

  14. there is a small mistake regarding the enzymatic activity of toxins. the exotoxins have enzymatic activity which can e denatured on heating while endotoxins being LPS has no enzymatic activity and has no effect of heating because of lipid nature.

    1. Your comment is correct. The lipopolysaccharide component of Gram negative bacterial cell wall has no enzymatic activity, and is chemically not related to the protein enzyme composition.

      Bacterial pyrogens are not affected by most sterilization processes, such as steam, ethylene gas, and gamma or electron beam irradiation.

  15. thank u sir!, iam a graduate of microbiology ur post r keeping me updated, sir can i be ur friend on facebook?

  16. It’s nice.and helpful

  17. Its informative nd very helpful.. I hope i ll get maximum Marks


  19. Very nice please enlight me more on this topic

    1. Learn something new….

  20. Nice job. Snd me request and I disecas from microbiology ok.

  21. Great to learn new things

  22. thank you so much. well, i would like you to collaborate more with explanation

  23. Iam a biotechnology student . It is very easy to understand .KEEP DOING IT.

  24. its perfect to differenciate………………

  25. I need you to help me find more information on why E.coli is sensitive to brilliant green. Thanks

  26. I am very very interesting for Microbiology study.

  27. Thank you for your great efforts

  28. Very nice…i really like to read all this posts…describe in simple n direct way…easy to understand….helping me in many ways …good work..keep doing it…m looking forward for some heamatology topics.

  29. Productive and fruitful information

  30. That cool, am a graduate of Microbiology, this question was part of the question asked from me during my seminar presentation. Was working on global health issue of Aflatoxin in food and agriculture. Its nice keep it up. Microbiology is all encompassing

  31. excellent. …

  32. if endotoxin found in liquid it is possible to remove??

  33. Thanks for the information..

  34. Hi…
    microbiology is a wonderful subject…
    good to see postings and notes… from you!

  35. Excellent notes.

  36. Excellent indeed.

  37. Well and updated information

  38. Really aws work helpful reading it

    1. Juss love reading dese posts put in simple but lucid manner enjoying n not boring

  39. I am a pharmacist. I am interested in microbiology and pharmacology related fields. Keeg it up!

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