Difference Between Endotoxins and Exotoxins (With Table)

Toxins are produced by pathogenic bacteria. Endotoxins are considered heat liable proteins that are specifically produced or secreted by certain species of gram bacteria. Exotoxins are lipopolysaccharide complex type of protein that is liberated after the death of bacteria. Both of these toxins vary from each other in chemical nature and other aspects as well. Endotoxins are consist of lipids and secreted by some specific species of bacteria. Exotoxins, on the other side, are consist of proteins.

Endotoxins vs Exotoxins

The difference between endotoxins and exotoxins is that endotoxins are a type of toxin released by gram bacteria, and it is present in the out sheath area of the cell wall. It is also called lipopolysaccharides. On the contrary, exotoxins are released with organism development. This type of toxin is contagious and may cause damage to various parts of the body. They are more toxic as compared to endotoxins. Even a single molecule can affect a large number of host cells.

Endotoxins are secreted or released from the outer area of the cell wall of bacteria after its death. These toxins are comprised of lipoglycan complex and are also called lipopolysaccharides. Endotoxins are moderately toxic and are not very active. Hence a large volume or amount of toxin is required to cause disease.

Exotoxins are the toxins that are produced or developed inside pathogenic bacteria as an integral part of their metabolism and growth. These are majorly produced by gram-negative bacteria and gram-positive bacteria. Exotoxins are highly toxic as a single molecule of toxin can act or affect a large number of host cells and cause harm to various parts or organs of the body.

Comparison Table Between Endotoxins and Exotoxins

Parameters of ComparisonEndotoxinsExotoxins
What is it?Endotoxins are released by an integral part of the cell wall of the bacteria and are mostly produced by gram-negative bacteriaExotoxins are developed or produced inside pathogenic bacteria as an integral part of their metabolism and growth
ToxicityThese toxins are moderately toxic These toxins are highly toxic
NeutralizationEndotoxins cannot be neutralized by antibodiesExotoxins can be neutralized by antibodies
DetectionThese types of toxins can be detected by limulus lysate assayThese toxins can be detected or located by many tests like precipitation, neutralization, etc.
Disease CausedDisease caused by endotoxins is sepsis by gram-negative rods, meningococcemia, etc..Diseases caused by exotoxins are diphtheria, botulism, tetanus, etc.

What is Endotoxins?

Endotoxins are released by an integral part of the cell wall of the bacteria and are mostly produced by gram-negative bacteria. These toxins are also called lipopolysaccharides. Endotoxins are mostly composed of three components including, O negative antigen, Lipid A, and core oligosaccharide.

Endotoxins are moderately toxic and not very active on their substrate. Its molecular weight is nearly 50-1000KDa. Catalase, lgG/IgA proteases, and catalyse are the enzymes present in these toxins. These toxins are secreted after the death of the bacteria. Endotoxins have low potency, and hence a large amount of toxin is required to affect a part or cause disease.

What is Exotoxins?

Exotoxins are developed or produced inside pathogenic bacteria as an integral part of their metabolism and growth. These toxins are produced by gram-negative bacteria and gram-positive bacteria. The molecular weight of these toxins is 10KDa. Exotoxins are composed of basically two subunits, A and B. Subunit A is nearly to have catalytic activity, while on the other side, subunit B is required for binding with the correct or appropriate cell receptors.

Nuclease, hyaluronidase, certain protease, collagenase, phospholipase A, neuraminidase are the enzymes present in exotoxins. These toxins are highly toxic. A single molecule can affect or act on a large number of host cells. These can be neutralized effectively by antibodies.

Main Differences Between Endotoxins and Exotoxins

  1. Toxins are produced by pathogens which are considered the root cause of several infections. Endotoxins and exotoxins both are toxins that are produced by different bacteria. Endotoxins are released by an integral part of the cell wall of the bacteria and are mostly produced by gram-negative bacteria. On the contrary, Exotoxins are developed or produced inside pathogenic bacteria as an integral part of their metabolism and growth.
  2. Endotoxins are composed of lipoglycan complex, and these are produced by gram-negative bacteria. On the other side, exotoxins are composed of polypeptides, and these toxins are majorly produced by two types of bacteria, namely gram-negative bacteria and gram-positive bacteria.
  3. Toxins are toxic, and their major role is to affect or cause harm to various parts of the organs. Endotoxins are moderately toxic, which means a large volume of toxins is required to cause disease. On the contrary, exotoxins are highly toxic, and a single molecule can affect a large number of host cells.
  4. Endotoxins and exotoxins are comprised of some specific components. Endotoxins are comprised or composed of three components including, O negative antigen, Lipid A, and core oligosaccharide. On the contrary, exotoxins are comprised of basically two subunits, A and B. Subunit A is near to have catalytic activity, while on the other side, subunit B is required for binding with the correct or appropriate cell receptor.
  5. Various diseases are caused due to these toxins that are produced by specific bacteria. Endotoxins cause diseases like sepsis by gram-negative rods, meningococcemia, etc. On the other side, diphtheria, botulism, tetanus, etc. are the disease caused by exotoxins.

Conclusion

Microbes play a vital role and are found everywhere in the living organism. Toxins are categorized into two types, endotoxins and exotoxins. These toxins are produced by some specific bacteria, and they lead to various diseases and infections. Enzymes and toxins are important in the pathogenicity of the pathogenic bacteria and may damage cells and can also trigger or damage the immune response.

References

  1. https://www.atsjournals.org/doi/abs/10.1164/ajrccm.156.3.9611010
  2. https://journals.asm.org/doi/abs/10.1128/iai.65.5.1767-1772.1997
  3. https://www.sciencedirect.com/science/article/pii/S0041010117303136
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