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Endotoxin and Exotoxin Difference

Last updated date: 27th Feb 2024
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An Introduction to Toxins: Explore Characteristics of Endotoxin and Exotoxin

In order to understand the difference between endotoxin and exotoxin, one must be aware of toxins and their types.

Meaning of Toxin

A chemical agent that harms an organism is referred to as a toxin. An ion or an atom that negatively affects a cell might be considered poison. Poison can also take the shape of intricate molecules, such as the proteins in snake venom. Still, other atoms and substances generate radiation, which harms living things.

Effect of Toxins

Toxins have a wide range of impacts on various creatures, depending on the toxin. Because the strongest toxins harm an organism's many cell types, their eventual effect is death. Toxins injure cells in various ways, depending on how they are affected.

Types of Toxins

A toxin can have a wide range of sizes and forms. A charged particle racing uncontrolled through the system and influencing other responses, or specialized proteins that specifically target the nervous system of a prey species might be the cause. It is hard to specify their size and shape because "toxin" is such a broad term. Animals often employ the toxins they create to control their prey or protect themselves from harm. They are therefore developed to especially affect some species. For instance, snake venom is a type of biological toxin made from a combination of several proteins.

What is Endotoxin and Exotoxin?

Endotoxin: Endotoxins are potentially hazardous complex chemicals that are frequently generated by Gram-negative bacteria. They were first identified in the late 19th century. Endotoxins, sometimes referred to as lipopolysaccharides (LPS), are among the most prevalent pyrogens (substances having the ability to cause fever).

They are a portion of the outer membrane of Gram-negative bacteria and consist of a hydrophilic polysaccharide and a hydrophobic substance (Lipid A).

Structure of Endotoxin

Endotoxins, as previously established, are made up of a polysaccharide attached to lipid A (a lipid moiety). Here, lipid A is in charge of the compound's hazardous side effects. For various Gram-negative bacteria, endotoxins have diverse structural characteristics. Because of this, the endotoxin's structure affects the degree of toxicity.

Exotoxin: Both Gram-negative and Gram-positive bacteria can release poisons known as exotoxins. They are extremely strong and, among other things, can interfere with normal biological functions to seriously harm host cells. Exotoxins may or may not be proteins depending on the bacterium. Similar to many other compounds, these toxins (such as botulinum neurotoxins) are created in the bacterial cytoplasm before being released into the extracellular environment. Some of these bacteria can also be discovered as intracellular pathogens inside the host cells. Toxins are thus immediately released into the host cells.

Structure of Exotoxin

Proteins make up the majority of exotoxins, which are created during exponential growth. Diffusible and soluble proteins make up exotoxins. Exotoxins have a significantly different molecular structure than endotoxins. Exotoxins come in a variety of forms, and there are still more that have not yet been identified.

Endotoxin and Exotoxin Difference 







Forms a portion of the cell wall and is released when bacteria die.

It is released as a result of metabolic processes.


Immune response

Relatively less capable of inducing an immunological response.

has a greater capacity to stimulate the immune system.



Composed of a combination of lipo glycans.

Contains polypeptides


Enzyme response

It doesn't engage in any enzymatic processes.

Enzymatic processes dominate most of the activity.



Unable to be transformed into toxoids.

Can be transformed into toxoids.



Infections of the urinary tract

Cardiovascular disease

Meningitis caused by bacteria

Scarlet fever


Scalded skin syndrome



Salmonella typhi (Typhoid),

Vibrio cholerae (Cholera).

Streptococcus pneumoniae (sepsis )

Clostridium botulinum (Botox),

Clostridium tetani (Tetanus),

Corynebacterium diphtheriae (Diphtheria).


Endotoxins are made largely of lipopolysaccharide molecules, whereas exotoxins are predominantly polypeptides. Comparing exotoxins to endotoxins, exotoxins are far more antigenic. Exotoxins have more receptor selectivity than endotoxins. Endotoxins lack enzymatic activity, but exotoxins do. The term toxoid is used to refer to inactivated toxins (suppressed toxicity). Toxoids can be generated from exotoxins but not from endotoxins. These toxins are typically employed as vaccines since they are changed (not generated naturally by the bacterium) in comparison to exotoxins. This is due to the fact that they can act as exotoxins and elicit an immunological response while being harmless.

FAQs on Endotoxin and Exotoxin Difference

1. What are the characteristics of Endotoxin?

Most Gram-negative bacteria have lipopolysaccharides on their outer membrane. However, some of these endotoxins are not virulent, and some of the species are not pathogenic, due to structural variations. While the compound's toxicity is linked to its lipid A component, the polysaccharide region is responsible for its immunogenicity, or ability to elicit an immune response. Lipopolysaccharides can be released in tiny amounts by Gram-negative bacteria, however, endotoxins are often less powerful than exotoxins.

2. What are the characteristics of Exotoxin?

Exotoxins can be secreted or, like endotoxins, can leak following cell lysis. However, certain exotoxins are so poisonous that they may kill the host before the immune system has an opportunity to establish defenses against them. Exotoxins are vulnerable to antibodies generated by the immune system. To give passive immunity in such circumstances, antitoxin, or anti-serum-carrying antibodies, may occasionally be administered. These exotoxins are secreted by bacteria into the environment as a defense against other pathogens.

3. Explain Endotoxin and Exotoxin.

The type of bacteria that release endotoxins and exotoxins is one of their primary distinctions. As previously stated, Gram-negative bacteria are responsible for producing endotoxins. Escherichia coli and Salmonella enterica are two examples of bacteria that have a thin cell wall and outer membrane.

However, both Gram-positive and Gram-negative bacteria can create exotoxins. Exotoxins come in a wide variety and have various mechanisms of action as a result. Gram-positive bacteria that can create exotoxin include Clostridium botulinum, whereas Gram-negative bacteria that may make exotoxin include Vibrio cholerae.