Biotoxins are poisonous substances produced from the metabolic processes of living organisms such as plants, animals, or microorganisms. Some toxins may also be produced or altered by chemical means. Unlike bacterial agents, toxins are not cellular organisms and cannot reproduce. Potential biological agents, biotoxins are generally stored in vials in lyophilized or powdered concentrate form. Most agents can be aerosolized or easily dissolved into water. Antibiotics may eliminate the biomaterial that produces the toxin but may not necessarily deactivate the toxin. Therapy to address the effects of toxins include antitoxin (antibody targeted towards a specific toxin) or antidotes (an agent used to counteract the poison by uniting with it to form a harmless compound).
Bacterial toxins are divided into two categories: endotoxins and exotoxins. Endotoxins are structural parts of the lipopolysaccharide (LPS) complex on a Gram-negative bacterium's cell wall. Exotoxins are generally poisonous proteins secreted by the bacteria. There are three ways these toxins affect cell processes. Membrane damaging toxins such as the Clostridium perfringens toxins produce destructive holes in the cell membrane. Membrane acting toxins such as E. coli attach themselves to the surface receptor of the cell membranes and disrupt signaling between cells. Intracellular acting toxins, a third category of toxins, enter the cell either by forcing entry themselves or being injected into the cell by the bacteria. Toxins that force entry (diphtheria, cholera, tetanus, botulinum, anthrax) bind to the cell, penetrate the membrane, and target specific functions in the cell. Toxins injected by bacteria such as plague and salmonella toxins may disrupt many cellular functions at once.
Many plant toxins are proteins constructed of peptide chains of amino acids. Other toxins include alkaloids, the organic nitrogen bearing chemical in hemlock and nightshade that typically act upon the nervous system. Alkaloids also include quinine and nicotine. Glycosides, another plant toxin found in foxgloves, are carbohydrates- usually sugar molecules attached to an uronic acid, joined to hydroxy molecules, a non-sugar entity such as alcohol or phenol. Oxalates such as arums or rhubarb are salts that release poisonous acids when digested. Phenols in nettles and poison ivy are acidic toxins that damage proteins. Resin toxins such as the oily sap of Poison Ivy and Poison Oak plants are hydrocarbons. Phototoxins, such as the poison found in St. John's Worts, increase skin sensitivity to sunlight.
Enterotoxins are toxins secreted by bacteria that disturb ion and water transport systems in the intestine to cause diarrhea. They are generally associated with food poisoning. Neurotoxins inhibit the workings of nervous system. Most animal venoms are neurotoxins. One type of neurotoxins is myotoxin, a toxin found in rattlesnake venom that induces muscle damage.
History of Toxins
Ancient texts described bacterial diseases such as tetanus, anthrax, diphtheria and cholera, but the concept of toxins was not developed until the late 19th Century. Friedrich Loeffler, a German bacteriologist working in Robert Koch's laboratory, discovered the bacteria Corynebacterium diphtheriae that causes diphtheria. The disease would begin as a leathery membrane that grew to constrict the throat, and the victim would die of suffocation unless a breathing passage was opened. Even if breathing was restored, general organ failure throughout the body would follow. Loeffler's bacteria, however, was only located in the throat of the victims and did not explain diphtheria symptoms throughout the body. Émile Roux and Alexandre Yersin, working in Louis Pasteur's laboratory, discovered that poisons released by the bacteria Corynebacterium diphtheriae caused diphtheria's other deadly symptoms.
Poisons have always been used as a weapon of war from poison arrows and dart to assassinations. It was recorded that one of the first uses of toxins as a biological agent was roughly 600 BCE when Solon, a legislator of the Athenians, oversaw the polluting of the Pleisthenes River with hellebores or skunk cabbage. The contaminated water spread violent diarrhea among the defenders of Kirrha. In 200 BCE, it was recorded that as a Carthaginian general retreated, he left behind wine mixed with Mandragons, a narcotic substance. When the enemies drank the wine and fell asleep, the Carthaginians returned and slaughtered them. Since these ancient methods, modern biotoxins such as ricin and saxitoxins continue to be used as a weapon of war and terror.
|Ricin||inhibits ribosomal protein synthesis||protein||caster plant Ricinus communi|
|Saxitoxin||sodium channels in nerve cells||neurotoxic alkaloids||freshwater and marine microalgae|
|Botulinum Toxins (Bacterial)||neuron membrane||proteins||bacteria: Clostridium botulinum|
|Clostridium Perfringens Toxins (Bacterial)||enterotoxins specific to intestinal cells||proteins||bacteria: Clostridium Perfringens|
|Staphylococcal Enterotoxin B (Bacterial)||enterotoxin specific to intestinal cells||protein||bacteria: Staphylococcus aureus|
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