29 Differences between Exotoxins and Endotoxins(With Table)

Microbiology is the study of microscopic organisms. These microorganisms are pathogenic since they produce toxins that cause infection.

These microbes are found everywhere whether inside and outside other living things. These toxins caused by these microorganisms are classified into endotoxin and exotoxin.

So, what is the main difference between exotoxins and endotoxins? The former is secreted as part of metabolisms while the latter is part of the cell wall and got released on the death of bacteria.

This article provides a detailed insight into the differences between exotoxins and endotoxins. The similarities also provide information on the relationship between exotoxins and endotoxins.

You May Also Enjoy: Difference between Gram-Positive and Gram-Negative Bacteria

Comparison Table (Exotoxins vs Endotoxins)

Basic Terms	Exotoxins	Endotoxins
Description	It is a protein produced inside a pathogen as part of growth and metabolism.	It is a lipopolysaccharide that is part of the outer membrane of bacteria.
Produced by	Both Gram-Positive and Negative bacteria.	Only Gram-Negative bacteria.
Chemical Nature	Protein (polypeptide) complexes	Lipopolysaccharide-protein complexes
Molecular weight	10KDa.	50-1000KDa.
Components	A subunit for catalytic activity. B subunit for binding with appropriate receptor cells.	O-antigen Core oligosaccharide Lipid A
Enzyme’s present	Hyaluronidase, Collagenase, certain protease, Nuclease, Neuraminidase, Certain protease, Phospholipase A	Catalase, Fibrolysin, IgA / IgG proteases
Chromosomal Location	Extrachromosomal genes	Chromosomal genes
Secreted by	Living cell	Lysed cell
Secretion	Outside the cell	Within the cell
Cell Lysis	Not necessary	Quite necessary
Stability to heat	Heat labile (60-80°C)	Heat stable (250°C)
Filtration	Filterable	Not Filterable
Boiling	Denatured	Not denatured
Enzyme Activity	Present	Limited or absent
Specificity	Highly specific since they are enzymes.	Not very specific in nature.
Specific receptors	Bind to specific receptors	Absent
Specificity to a bacterial strain	Yes	No
Immunogenicity	Highly immunogenic.	Weakly immunogenic.
Fever Induction	No	Induced by interleukin 1 (IL-1) production.
Toxicity	Highly toxic	Moderate toxic
Mode of action	Various modes	Includes TNF and Interlukin-1
Potency	High	Low
Effects	Either cytotoxin, enterotoxin, or neurotoxin with defined action on cells	Fever, diarrhea, vomiting
Neutralization by Antibodies	Can be neutralized	Cannot be neutralized
Detection	Through tests such as neutralization and precipitation.	Limulus lysate assay.
Conversion to Toxoids	Treatment by formalin	Not possible.
Availability of vaccines	Available	Not available
Diseases	Tetanus, diphtheria, botulism, etc.	Meningococcemia, sepsis by gram-negative rods, etc.
Examples	Staphylococcus aureus, Bacillus cereus, Streptococcus pyogenes, Bacillus anthracis	E.coli, Salmonella Typhi, Shigella, Vibrio cholera

What Is Exotoxins?

Exotoxins are types of toxic substances that are released extracellularly. Exotoxins have the ability to spread to other parts from a focus infection causing a lot of damage.

Research shows that it is the most lethal toxic condition as compared to endotoxins. It normally occurs in three forms as Neurotoxin, Enterotoxin, and Cytotoxin.

Exotoxins only cause diseases that are specifically caused by that contamination. Some of the common health disorders caused by exotoxins are Cholera, tetanus, and Diphtheria.

What Is Endotoxins?

Endotoxins are a type of toxic substance that spread into the surrounding medium and causing a lot of damage to the host by disrupting the normal function of the cell.

Also, they are heat stable liable proteins that form the structural component of the cell wall of the gram-negative bacteria. They are only liberated on cell lysis or the death of bacteria.

Endotoxins are quite common in Vibrio cholera, Neisseria, E Coli, Pseudomonas, Salmonella, Haemophilus influenza, and Shigella.

Differences Between Exotoxins and Endotoxins

Exotoxins are secreted by the living cell while endotoxins are an integral part of the cell wall.
Exotoxins are found in both gram-positive bacteria and gram-negative bacteria whereas endotoxins are found only in gram-negative bacteria
Exotoxins are a simple polypeptide while endotoxins is a complex lipopolysaccharide
Exotoxins are relative heat liable at 60 degrees hence quite unstable while endotoxins are heat tolerant even at 100 degrees
Endotoxins are weak immunogenic while exotoxins are highly antigenic
Exotoxins releases toxoid used in treating with formalin while endotoxin cannot make toxoid.
Exotoxins are highly toxic and fatal while endotoxins are moderately toxic and fatal
Exotoxins are normally bound to specific receptors while endotoxins are not bound to specific receptors.
Endotoxins are located on chromosomal genes while exotoxins are located on extrachromosomal genes.
Exotoxins get denatured when exposed to high boiling points while endotoxins do not get denatured even after exposure to high boiling points.
Examples of diseases caused by exotoxins are Tetanus, diphtheria, and botulism while those caused by endotoxins are Meningococcemia and sepsis by gram-negative rods.
Endotoxin produce fever in the host whereas exotoxin does not
There are effective vaccines for exotoxins whereas there are no effective vaccines for endotoxins
Exotoxins are very lethal even in minute quantities whereas endotoxins are very lethal in large quantities
Exotoxins use specific receptors to enter the host cells while endotoxins have no specific receptors
Exotoxin show affinity towards specific tissues while endotoxin does not show affinity towards specific tissues
The molecular weight of exotoxin is 10KDa whereas the molecular weight of endotoxin is about 50-1000KDa
Exotoxins are filterable whereas endotoxins are not
Exotoxin has the ability to trigger immune responses whereas endotoxin cannot trigger an immune response
Exotoxin tends to stay active beyond 60 degrees whereas endotoxin tends to stay active beyond 100 degrees Celcius.

Similarities between Exotoxins and Endotoxins

Both are brought about by bacteria
Both cause diseases to the host
Both are located on chromosomes
Both are toxic
Both can be affected by heat

Frequently Asked Question

Is Tetanus an Endotoxin or Exotoxin?

Exotoxin. They are mainly bound to the bacterial body that develops their pathogenic effects only after bacterial cell decay.

Are Endotoxins More Potent than Exotoxins?

Endotoxins are less potent and less specific. They are normally released and not secreted. They tend to disrupt the normal functioning of the cell.

Why are Endotoxins Dangerous?

Dangerous endotoxins are released by gram-negative bacteria. Once they are released into the body, they weaken the immune system by attacking antibodies.

Is Endotoxin Gram-Positive or Negative?

Gram-negative bacteria.

Are Exotoxins Gram-Positive or Negative?

Both gram-positive and gram-negative. They are secreted by both gram-positive and gram-negative bacteria.

You May Also Like:

Conclusion

Toxic substances are chemical components produced by the bacteria to cause damages to the host and also diseases. They occur in the form of exotoxins and endotoxins.

Exotoxins are fatal in small quantities while endotoxins are relatively less fatal. The differences between exotoxins and endotoxins listed above are suitable for you.

More Sources and References

Exotoxin.Wikipedia
Exotoxins and Endotoxins. NCBI