• Toxins are deadly compounds released by living cells or creatures. They can be tiny molecules or proteins of various types that cause sickness when they come into contact. Toxins can trigger a variety of ailments, ranging in degree and kind from mild to fatal. Bacteria, fungus, algae, and plants are examples of microorganisms that may produce poisons. 
  • Environmental, marine, and microbiological toxins are only a few examples of the various types of toxins. Toxins generated by bacteria (bacterial toxins) and fungus (fungal toxins) are examples of microbial toxins (i.e. mycotoxins).
  • It can be broadly described as a naturally occurring chemical that has been identified as harmful to some form of life.
  • A toxin, just like every other molecule, has a specific molecular weight, elemental constitution, and covalent structure.
  • Toxic compounds produced by human hands (and thoughts) are popularly referred to as poisons. Toxins can be made for internal use, such as complement proteins and defensin peptides, which aid in the defense of our bodies against infectious illnesses.
  • To paralyze prey or survive a predator attack, several poisons operate quickly on their victims. Electrically excitable cells, such as nerves and muscles (particularly the heart), are affected by rapidly acting toxins as they are required for movement, respiration, and cardiovascular function. Voltage-gated sodium, calcium, and potassium ion-passing channels involved in the formation of action potentials, as well as ligand-gated ion channels found at synapses and open in response to a neurotransmitter, are among the toxins’ cellular targets (receptors). These ion channels are membrane proteins that open in response to a change in the membrane’s electrical potential or the abrupt presence of a neurotransmitter.
  • When a poisonous chemical comes into touch with or is absorbed by bodily tissues, it causes severe damage to the organism. These substances interact with different sections of the body. Toxins have a wide range of effects, ranging from small yet acute (bee stings) to virtually instantaneously fatal (botulinum).

Classification of toxins based on the targeted part of our body

They can be categorized based on where on the body their effects are most noticeable:

 Types of Toxins

They can be categorized based on where on the body their effects are most evident which are:

  1. Hemotoxins(found in some snakes, for example) kill red blood cells and cause tissue damage.
  2. Photo-toxins(such as alpha-terthienyl, which can be present in marigold plants) might trigger allergic responses in those who are sensitive to them.
  3. Necro-toxins(for example, necrotizing fasciitis – germs that devour flesh) kill cells and cause tissue damage in general. Sand spiders in South Africa have necrotic venom.
  4. Neurotoxins(such as tetrodotoxin, which is present in pufferfish and some grey side-gilled sea slugs) impact an organism’s neurological system. Neurotoxins are used by black widow spiders.

Classification of toxins based on their origin


  • Bacterial Toxins: 

Due to the difficulties of collecting and growing marine bacteria, toxins and other natural compounds contained in these organisms were mostly unknown until recently. However, it is now clear that the bacterial variety of the marine environment is quite significant, and that the organisms are not as comparable to those found on land as previously supposed. Colonial bacteria were discovered in blue-green algae, several of which carry poisons (cyanobacteria). Many of the poisons detected in marine creatures are actually produced by symbiotic bacteria living within their tissues, it has been discovered. Tetrodotoxin (TTX), palytoxin, ciguatera toxin, and okadaic acid are all strong toxins that can cause severe illness and even death in humans.

Types of Bacterial Toxin

Bacterial toxins are classified into two groups:

  1. Exotoxin 
  2. Endotoxin
  • Bacterial Exotoxins are proteins that gram-positive and gram-negative bacteria make and release extracellularly. these are heat-labile, soluble proteins that are generated primarily in the environment where bacteria thrive. Exotoxin can be rendered inactive at temperatures ranging from 60 to 80 degrees Celsius. Botulism, gas gangrene, tetanus, diphtheria, staphylococcal food poisoning, cholera, enterotoxins, and plague are all examples of diseases.

Exotoxin properties of bacteria:

Gram-positive bacteria create the majority of exotoxins, however, a few Gram-negative bacteria are also involved. Exotoxins are secreted outside of the cell. Exotoxins are made up of polypeptides chemically. Exotoxins are denatured at temperatures over 60 degrees Celsius and by UV radiation. One of the most powerful poisons is exotoxins. Exotoxins can be a hundred to one million times stronger than strychnine. Exotoxin is a highly specialized toxin that can operate as a neurotoxic or a toxin of the heart muscle. Exotoxin has a high antigenicity, which means it can boost antibody formation and immunity.

  1. Bacterial Endotoxin is a kind of endotoxin produced by bacteria. Endotoxins are a kind of lipopolysaccharide found in Gram-Negative bacteria’s outer membrane. When a microbe lyses, endotoxin is produced, and it can also be secreted during cell division. The lipid is a kind of fat. Endotoxin poisoning is caused by a protein found in the LPS. Salmonellosis, tularemia, and endotoxic shock are only a few examples.

Endotoxin properties of bacteria:

Gram-negative bacteria are the principal producers of endotoxins. Endotoxins are toxins that are bound within the bacterial cell wall and released when the organism dies. Lipopolysaccharide complexes make up the majority of endotoxin. Endotoxins are relatively stable and can survive temperatures of up to 60 degrees Celsius for several hours. Although endotoxin has low toxicity, it can be lethal in large concentrations. Endotoxin has a non-specific impact. A high fever or temperature can be caused by endotoxin.

  • Mycotoxins

Toxins generated by fungus are known as mycotoxins. Mycotoxins come in a variety of forms, and their production is not limited to a single species. Mycotoxins are fungi-produced secondary metabolites that are hazardous to humans. A wide range of mycotoxins exist, including aflatoxins, ochratoxins, citrinin, and ergot alkaloids, to name a few.

  • Aflatoxins

Aflatoxins are a form of mycotoxin generated by specific Aspergillus fungus strains. There are four different forms of aflatoxins: AFB1, AFB2, AFG1, and AFG2. These strains can be found in a wide range of agricultural products from the tropics and subtropics. Peanut and corn species are among these products. AFB1, the most powerful toxin, has been linked to carcinogenic consequences.

  • Ochratoxin

Both Penicillium and Aspergillus species generate ochratoxin, a kind of toxin. Ochratoxins are divided into three types: A, B, and C, each with its own structure. Ochratoxins have been shown to cause cancer and are commonly detected in drinks such as beer and wine, as the fungal species that create ochratoxins are frequently found on the plants that produce these goods.

  • Citrinin

Citrinin is a mycotoxin that has been found in a variety of Penicillium and Aspergillus species. Many of these fungi are used in food processing and may be found in cheese, wheat, rice, maize, and soy sauce, among other things. Citrinin is a nephrotoxic, meaning it has a harmful impact on kidney function.

  • Ergot Alkaloids

Claviceps, a fungus associated with grasses, rye, and allied plants, produces ergot alkaloids, which are unique chemicals created as poisonous alkaloids. Ergotism is a sickness induced by eating of this fungus. Ergotism is characterized by negative effects on the vascular system, including vasoconstriction of blood vessels, which can lead to gangrene and, if left untreated, limb loss. Additionally, because ergot alkaloids target the central nervous system, ergotism can manifest as hallucinations and convulsions. Ergot alkaloids have been employed for medical reasons because of their effects on the vascular system.

Key Notes

  • Endotoxin is a poison secreted by a bacterium that is only released into the environment after the organism dies.
  • Exotoxin: Any poison produced into the environment by a bacterium is known as an exotoxin.
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