Differences Between Exotoxins and Endotoxins 4.63/5 (825)

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 cell Integral part of cell wall


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


It is polypeptide It is lipopolysaccharide complex.


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


Highly antigenic Weakly immunogenic


Toxoids can be madeby treating with formalin Toxoids cannot be made


Highly toxic, fatal in µg quantities Moderately toxic


Usually binds to specific receptors Specific receptors not found


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


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


Filterable Not so


It has no enzymatic activity It has mostly enzymatic activity


Its molecular weight is 10KDa Its 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, botulism Diseases: Meningococcemia, sepsis by gram negative rods

Differences Between Exotoxins and Endotoxins

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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 Lecturer at Department of Microbiology, 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 !!!


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  1. from jomokenyatta university, Jkuat, Kenya, indeed very useful information to us as student pursuing health sciences

  2. syed kashif hussain

    good difference

  3. its very usefull for me i am very confused difference between exo&endotoxin bt now i am very clear thanks for your information

  4. am a pharmacy studant from sudan

    thank for this’s informations

  5. Thank you so much sir for such a good notes.

  6. Hi my name is jolade a food safety officer. Loved your write up. But wondered if you can make it a little bit clearer in plain english. Could raw food contain endotoxin and since it is heat stable that means it cannot be killed by cooking. What primarily should I advice food business to do to prevent endotoxins in food.
    My son just suffered from severe gastroentrititis.
    Many thanks

  7. I am a student of microbiology…nice write up but my question goes this way…
    Why is exotoxin highly antigenic and endotoxins weakly immunogenic since the molecular weight of endotoxins(50-1000kDa) is greater than that of exotoxins(10kDa)?

  8. This is sooo amazing thank u soo much i wasnt getting the difference but now am well educated on it i believe i can teach someone as well…thanks may God bless u

  9. André Vicente Oliveira da Silva

    World workers (researchers, scientists, academics) need to integrate within new discoveries for!

    Mondskalaj gelaboristoj necesas interliĝi pri novaj serĉadoj

  10. muhammad abubakar umar

    want to join microbiology society

  11. its is inspiring and excellent too

  12. thanks for nice notes

  13. Thanks sir it enriching.

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

  15. 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

  16. rakesh chowdhary

    thanks a lot sir

  17. rajesh kumar mishra

    Thnku for this valuable notes

  18. Important informations..great thanks

  19. very nice thanks

  20. 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. muhammad ali chandio

      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

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

  22. 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.

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

  24. It’s nice.and helpful

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


  27. Very nice please enlight me more on this topic

    1. Learn something new….

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

  29. Great to learn new things

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

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

  32. its perfect to differenciate………………

  33. Akinrotoye kehinde Peter

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

  34. I am very very interesting for Microbiology study.

  35. Thank you for your great efforts

  36. 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.

  37. Rafique Ahmed Channa

    Productive and fruitful information

  38. shogbuyi olamide

    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

  39. excellent. …

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

  41. Thanks for the information..

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

  43. Excellent notes.

  44. Excellent indeed.

  45. Mumtaz Ali Sanjrani

    Well and updated information

  46. Really aws work helpful reading it

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

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

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