Cyanotoxin - AbsoluteAstronomy.com

Cyanotoxins are toxin

Toxin

A toxin is a poisonous substance produced within living cells or organisms; man-made substances created by artificial processes are thus excluded...

s produced by bacteria called cyanobacteria (also known as blue-green algae). Cyanobacteria are found almost everywhere, but particularly in lakes and in the ocean where, under certain conditions, they reproduce exponentially

Exponential growth

Exponential growth occurs when the growth rate of a mathematical function is proportional to the function's current value...

to form blooms

Algal bloom

An algal bloom is a rapid increase or accumulation in the population of algae in an aquatic system. Algal blooms may occur in freshwater as well as marine environments. Typically, only one or a small number of phytoplankton species are involved, and some blooms may be recognized by discoloration...

. Blooming cyanobacteria can produce cyanotoxins in such concentrations that they poison

Poison

In the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism....

and even kill animals and humans. Cyanotoxins can also accumulate in other animals such as fish and shellfish

Shellfish

Shellfish is a culinary and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms. Although most kinds of shellfish are harvested from saltwater environments, some kinds are found only in freshwater...

, and cause poisonings such as shellfish poisoning

Shellfish poisoning

There are four syndromes called shellfish poisoning, which share some common features and are primarily associated with bivalve molluscs...

.

Among cyanotoxins are some of the most powerful natural poisons known, including poisons which can cause rapid death by respiratory failure. The toxins include potent neurotoxins, hepatotoxins, cytotoxins, and endotoxins. Recreational exposure to cyanobacteria can result in gastro-intestinal and hayfever symptoms or pruritic skin rashes. There is some evidence that significant exposure to high levels of some species of cyanobacteria causes Lou Gehrig's disease

Amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis , also referred to as Lou Gehrig's disease, is a form of motor neuron disease caused by the degeneration of upper and lower neurons, located in the ventral horn of the spinal cord and the cortical neurons that provide their efferent input...

. There is also an interest in the military potential of biological neurotoxins such as cyanotoxins, which "have gained increasing significance as potential candidates for weaponization."

The first published report that blue-green algae or cyanobacteria could have lethal effects appeared in Nature
Nature (journal)
Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...

in 1878. George Francis described the algal bloom he observed in the estuary of the Murray River

Murray River

The Murray River is Australia's longest river. At in length, the Murray rises in the Australian Alps, draining the western side of Australia's highest mountains and, for most of its length, meanders across Australia's inland plains, forming the border between New South Wales and Victoria as it...

in Australia, as "a thick scum like green oil paint, some two to six inches thick." Wildlife which drank the water died rapidly and terribly. Most reported incidents of poisoning by microalgal toxins have occurred in freshwater environments, and they are becoming more common and widespread. For example, thousands of ducks and geese died drinking contaminated water in the midwestern United States. In 2010, for the first time, marine mammals were reported to have died from ingesting cyanotoxins.

Cyanobacteria

Cyanotoxins are produced by cyanobacteria, a phylum of bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

that obtain their energy through photosynthesis

Photosynthesis

Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

. The prefix cyan
Cyan
Cyan from , transliterated: kýanos, meaning "dark blue substance") may be used as the name of any of a number of colors in the blue/green range of the spectrum. In reference to the visible spectrum cyan is used to refer to the color obtained by mixing equal amounts of green and blue light or the...

comes from the Greek

Greek language

Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

κύανoς meaning "a dark blue substance", and usually indicates any of a number of colours in the blue/green range of the spectrum. Cyanobacteria are commonly referred to as blue-green algae. Traditionally they were thought of as a form of algae, and were introduced as such in older textbooks. However modern sources tend to regard this as outdated; they are now considered to be more closely related to bacteria, and the term for true algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

is restricted to eukaryotic

Eukaryote

A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...

organisms. Like true algae, cyanobacteria are photosynthetic and contain photosynthetic pigment

Photosynthetic pigment

A photosynthetic pigment is a pigment that is present in chloroplasts or photosynthetic bacteria and captures the light energy necessary for photosynthesis.- Plants :...

s, which is why they are usually green or blue.

Cyanobacteria are found almost everywhere; in oceans, lakes and rivers as well as on land. They flourish in Arctic and Antarctic lakes, hotsprings and wastewater

Wastewater

Wastewater is any water that has been adversely affected in quality by anthropogenic influence. It comprises liquid waste discharged by domestic residences, commercial properties, industry, and/or agriculture and can encompass a wide range of potential contaminants and concentrations...

treatments plants. They even inhabit the fur of polar bears, to which they impart a greenish tinge. Cyanobacteria produce potent toxins, but they also produce helpful bioactive compounds, including substances with antitumour, antiviral, anticancer, antibiotic and antifungal activity, UV protectants and specific inhibitors of enzymes

Enzyme inhibitor

An enzyme inhibitor is a molecule that binds to enzymes and decreases their activity. Since blocking an enzyme's activity can kill a pathogen or correct a metabolic imbalance, many drugs are enzyme inhibitors. They are also used as herbicides and pesticides...

Harmful algal blooms

Cyanotoxins are often implicated in what are commonly called red tide
Red tide
Red tide is a common name for a phenomenon also known as an algal bloom , an event in which estuarine, marine, or fresh water algae accumulate rapidly in the water column and results in discoloration of the surface water. It is usually found in coastal areas...

s or harmful algal blooms. Lakes and oceans contain many single-celled organisms called phytoplankton

Phytoplankton

Phytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words φυτόν , meaning "plant", and πλαγκτός , meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye...

. Under certain conditions, particularly when nutrient concentrations are high, these organisms reproduce exponentially

Exponential growth

Exponential growth occurs when the growth rate of a mathematical function is proportional to the function's current value...

. The resulting dense swarm of phytoplankton is called an algal bloom

Algal bloom

; these can cover hundreds of square kilometres and can be easily seen in satellite images. Individual phytoplankton rarely live more than a few days, but blooms can last weeks.

Generally these blooms are harmless, but if not they are called harmful algal blooms, or HABs. HABs can contain toxins or pathogens which result in fish kill

Fish kill

The term fish kill, known also as fish die-off and as fish mortality, is a localized die-off of fish populations which may also be associated with more generalised mortality of aquatic life...

and can also be fatal to humans. In marine environments, HABs are mostly caused by dinoflagellate

Dinoflagellate

The dinoflagellates are a large group of flagellate protists. Most are marine plankton, but they are common in fresh water habitats as well. Their populations are distributed depending on temperature, salinity, or depth...

s, though species of other algae taxa can also cause HABs (diatom

Diatom

Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...

s, flagellate

Flagellate

Flagellates are organisms with one or more whip-like organelles called flagella. Some cells in animals may be flagellate, for instance the spermatozoa of most phyla. Flowering plants do not produce flagellate cells, but ferns, mosses, green algae, some gymnosperms and other closely related plants...

s, haptophyte

Haptophyte

The haptophytes, classified either as the Prymnesiophyta or Haptophyta, are a division of algae.The term "Haptophyceae" is sometimes used. This ending implies classification at a lower level...

s and raphidophyte

Raphidophyte

Raphidophytes are a small group of eukaryotic algae that includes both marine and freshwater species. All raphidophytes are unicellular, with large cells but no cell walls. Raphidophytes possess a pair of flagella, organised such that both originate from the same invagination...

s). Marine dinoflagellate species are often toxic, but freshwater species are not known to be toxic. Neither are diatoms known to be toxic, at least to humans.

Cyanobacteria also commonly produce blooms and HABs. Cyanobacteria species are often toxic, and in freshwater ecosystems are the most common cause of eutrophication

Eutrophication

Eutrophication or more precisely hypertrophication, is the movement of a body of water′s trophic status in the direction of increasing plant biomass, by the addition of artificial or natural substances, such as nitrates and phosphates, through fertilizers or sewage, to an aquatic system...

. Their blooms can look like foam, scum or mats or like paint floating on the surface of the water, but they are not always visible. Nor are the blooms always green; they can be blue, and some cyanobacteria species are coloured brownish-red. The water can become malodorous when the cyanobacterial in the bloom die.

Strong cyanobacterial blooms reduce visibility to one or two centimetres. Species which do not need to see to migrate

Diel vertical migration

Diel vertical migration, also known as diurnal vertical migration, is a pattern of movement that some organisms living in the ocean and in lakes undertake each day. Usually organisms move up to the epipelagic zone at night and return to the mesopelagic zone of the oceans or to the hypolimnion zone...

in the water column (such as the cyanobacteria themselves) survive, but species which need to see to find food and partners are compromised. During the day blooming cyanobacteria saturate the water with oxygen. At night respiring aquatic organisms can deplete the oxygen to the point where sensitive species, such as certain fish, die. This is more likely to happen near the sea floor or a thermocline

Thermocline

A thermocline is a thin but distinct layer in a large body of fluid , in which temperature changes more rapidly with depth than it does in the layers above or below...

. Water acidity also cycles daily during a bloom, with the pH reaching 9 or more during the day and dropping to low values at night, further stressing the ecosystem. In addition, many cyanobacteria species produce potent cyanotoxins which concentrate during a bloom to the point where they become lethal to nearby aquatic organisms and any other animals in direct contact with the bloom, including birds, livestock, domestic animals and sometimes humans.

In 1991 a harmful cyanobacterial bloom affected 1000 km of the Darling

Darling River

The Darling River is the third longest river in Australia, measuring from its source in northern New South Wales to its confluence with the Murray River at Wentworth, New South Wales. Including its longest contiguous tributaries it is long, making it the longest river system in Australia.The...

-Barwon

Barwon River (New South Wales)

The Barwon River flows through New South Wales, virtually as a continuation of the Macintyre River / Border Rivers system, before joining with the Culgoa River to form the Darling River...

River in Australia at an economic cost of $10M AUD.

Chemical structure

The chemical structure of cyanotoxins falls into three broad groups: cyclic peptides, alkaloids
and lipopolysaccharides.

Chemical structure of cyanotoxins
Structure	Cyanotoxin	Primary target organ in mammals	Cyanobacteria genera
Cyclic peptide Cyclic peptide Cyclic peptides are polypeptide chains whose amino and carboxyl termini are themselves linked together with a peptide bond that forms a circular chain. A number of cyclic peptides have been discovered in nature and they can range anywhere from just a few amino acids in length, to hundreds... s	Microcystin Microcystin Microcystins are cyclic nonribosomal peptides produced by cyanobacteria . They are cyanotoxins and can be very toxic for plants and animals including humans. Their hepatotoxicity may cause serious damage to the liver. Microcystins can strongly inhibit protein phosphatases type 1 and 2A , and are... s	Liver	Microcystis Microcystis Microcystis is the genus of freshwater cyanobacteria which includes the harmful algal bloom Microcystis aeruginosa.-Etymology:The generic moniker Microcystis derives from the Greek mikros + kystis... , Anabaena Anabaena Anabaena is a genus of filamentous cyanobacteria that exists as plankton. It is known for its nitrogen fixing abilities, and they form symbiotic relationships with certain plants, such as the mosquito fern. They are one of four genera of cyanobacteria that produce neurotoxins, which are harmful to... , Planktothrix Planktothrix Planktothrix is a genus of filamentous blue-green algae. Type species of the genus Planktothrix is Planktothrix agardhii Anagnostidis & Komárek. The genus was scrutinized in 2002 by S. Suda . Before, some species of the taxon were grouped within the genus Oscillatoria.- Species :* Planktothrix... (Oscillatoria), Nostoc Nostoc Nostoc is a genus of cyanobacteria found in a variety of environmental niches that forms colonies composed of filaments of moniliform cells in a gelatinous sheath.The name "Nostoc" was invented by Paracelsus... , Hapalosiphon, Anabaenopsis
	Nodularin Nodularin Nodularin-R is a cyclic nonribosomal peptide produced by the planktonic cyanobacterium Nodularia spumigena. This cyanobacterium forms blooms in brackish water bodies throughout the world. The late summer blooms of Nodularia spumigena are among the largest cyanobacterial mass occurrences in the world... s	Liver	Nodularia Nodularia Nodularia is a genus of filamentous nitrogen-fixing cyanobacteria, or blue-green algae. They occur mainly in brackish or salinic waters, such as the hypersaline Makgadikgadi Pans, the Peel-Harvey Estuary in Western Australia or the Baltic Sea. Nodularia cells occasionally form heavy algal blooms...
Alkaloid Alkaloid Alkaloids are a group of naturally occurring chemical compounds that contain mostly basic nitrogen atoms. This group also includes some related compounds with neutral and even weakly acidic properties. Also some synthetic compounds of similar structure are attributed to alkaloids... s	Anatoxin-a Anatoxin-a Anatoxin-a, also known as Very Fast Death Factor, is a secondary, bicyclic amine alkaloid and cyanotoxin with acute neurotoxicity. The toxin is produced by at least four different genera of cyanobacteria and has been reported in North America, Europe, Africa, Asia, and New Zealand. The toxin is...	Nerve synapse	Anabaena Anabaena Anabaena is a genus of filamentous cyanobacteria that exists as plankton. It is known for its nitrogen fixing abilities, and they form symbiotic relationships with certain plants, such as the mosquito fern. They are one of four genera of cyanobacteria that produce neurotoxins, which are harmful to... , Planktothrix Planktothrix Planktothrix is a genus of filamentous blue-green algae. Type species of the genus Planktothrix is Planktothrix agardhii Anagnostidis & Komárek. The genus was scrutinized in 2002 by S. Suda . Before, some species of the taxon were grouped within the genus Oscillatoria.- Species :* Planktothrix... (Oscillatoria), Aphanizomenon Aphanizomenon Aphanizomenon is an important genus of cyanobacteria that inhabits freshwater lakes and can cause choking blooms. Studies on the species Aphanizomenon flos-aquae have shown that it can regulate buoyancy through light-induced changes in turgor pressure...
	Anatoxin-a(S)	Nerve synapse	Anabaena Anabaena Anabaena is a genus of filamentous cyanobacteria that exists as plankton. It is known for its nitrogen fixing abilities, and they form symbiotic relationships with certain plants, such as the mosquito fern. They are one of four genera of cyanobacteria that produce neurotoxins, which are harmful to...
	Aplysiatoxin Aplysiatoxin Aplysiatoxin is a cyanotoxin produced by certain cyanobacteria species. It is used as a defensive secretion to protect these cyanobacteria from predation by fish, being a potent irritant and carcinogen, by acting as a powerful activator of Protein kinase C... s	Skin	Lyngbya Lyngbya Lyngbya is a genus of cyanobacteria, unicellular autotrophs that form the basis of the oceanic food chain.Lyngbya form long unbranching filaments inside a rigid mucilage sheath. Sheaths may form tangles or mats, intermixed with other phytoplankton species... , Schizothrix, Planktothrix Planktothrix Planktothrix is a genus of filamentous blue-green algae. Type species of the genus Planktothrix is Planktothrix agardhii Anagnostidis & Komárek. The genus was scrutinized in 2002 by S. Suda . Before, some species of the taxon were grouped within the genus Oscillatoria.- Species :* Planktothrix... (Oscillatoria)
	Cylindrospermopsin Cylindrospermopsin Cylindrospermopsin is a cyanotoxin produced by a variety of freshwater cyanobacteria. CYN is a polycyclic uracil derivative containing guanidino and sulfate groups. It is also zwitterionic, making it highly water soluble. CYN is toxic to liver and kidney tissue and is thought to inhibit protein... s	Liver	Cylindrospermopsis, Aphanizomenon Aphanizomenon Aphanizomenon is an important genus of cyanobacteria that inhabits freshwater lakes and can cause choking blooms. Studies on the species Aphanizomenon flos-aquae have shown that it can regulate buoyancy through light-induced changes in turgor pressure... , Umezakia
	Lyngbyatoxin-a Lyngbyatoxin-a Lyngbyatoxin-a is a cyanotoxin produced by certain cyanobacteria species, notably Lyngbya majuscula. It is used as a defensive secretion to protect this cyanobacteria from predation by fish, being a potent irritant and vesicant, as well as a carcinogen. Low concentrations more commonly encountered...	Skin, gastro-intestinal tract	Lyngbya Lyngbya Lyngbya is a genus of cyanobacteria, unicellular autotrophs that form the basis of the oceanic food chain.Lyngbya form long unbranching filaments inside a rigid mucilage sheath. Sheaths may form tangles or mats, intermixed with other phytoplankton species...
	Saxitoxin Saxitoxin Saxitoxin is a neurotoxin naturally produced by certain species of marine dinoflagellates and cyanobacteria Saxitoxin (STX) is a neurotoxin naturally produced by certain species of marine dinoflagellates (Alexandrium sp., Gymnodinium sp., Pyrodinium sp.) and cyanobacteria Saxitoxin (STX) is a... s	Nerve axons	Anabaena Anabaena Anabaena is a genus of filamentous cyanobacteria that exists as plankton. It is known for its nitrogen fixing abilities, and they form symbiotic relationships with certain plants, such as the mosquito fern. They are one of four genera of cyanobacteria that produce neurotoxins, which are harmful to... , Aphanizomenon Aphanizomenon Aphanizomenon is an important genus of cyanobacteria that inhabits freshwater lakes and can cause choking blooms. Studies on the species Aphanizomenon flos-aquae have shown that it can regulate buoyancy through light-induced changes in turgor pressure... , Lyngbya Lyngbya Lyngbya is a genus of cyanobacteria, unicellular autotrophs that form the basis of the oceanic food chain.Lyngbya form long unbranching filaments inside a rigid mucilage sheath. Sheaths may form tangles or mats, intermixed with other phytoplankton species... , Cylindrospermopsis
Lipopolysaccharide Lipopolysaccharide Lipopolysaccharides , also known as lipoglycans, are large molecules consisting of a lipid and a polysaccharide joined by a covalent bond; they are found in the outer membrane of Gram-negative bacteria, act as endotoxins and elicit strong immune responses in animals.-Functions:LPS is the major... s		Potential irritant; affects any exposed tissue	All

Most cyanotoxins have a number of variants (analogues). Altogether over 84 cyanotoxins are known although only a small number have been well studied.

Cyclic peptides

A peptide

Peptide

Peptides are short polymers of amino acid monomers linked by peptide bonds. They are distinguished from proteins on the basis of size, typically containing less than 50 monomer units. The shortest peptides are dipeptides, consisting of two amino acids joined by a single peptide bond...

is a short polymer

Polymer

A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...

of amino acid

Amino acid

Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...

s linked by peptide bond

Peptide bond

This article is about the peptide link found within biological molecules, such as proteins. A similar article for synthetic molecules is being created...

s. They have the same chemical structure as protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

s, except they are shorter. In a cyclic peptide

Cyclic peptide

Cyclic peptides are polypeptide chains whose amino and carboxyl termini are themselves linked together with a peptide bond that forms a circular chain. A number of cyclic peptides have been discovered in nature and they can range anywhere from just a few amino acids in length, to hundreds...

the links link back to the start to form a stable circular chain. In mammals this stability makes them resistant to the process of digestion and they can bioaccumulate in the liver. Of all the cyanotoxins, the cyclic peptides are of most concern to human health. The microcystins and nodularins poison the liver, and exposure to high doses can cause death. Exposure to low doses in drinking water over a long period of time may promote liver and other tumours.

Microcystins

As with other cyanotoxins, microcystin

Microcystin

Microcystins are cyclic nonribosomal peptides produced by cyanobacteria . They are cyanotoxins and can be very toxic for plants and animals including humans. Their hepatotoxicity may cause serious damage to the liver. Microcystins can strongly inhibit protein phosphatases type 1 and 2A , and are...

s were named after the first organism discovered to produce them, Microcystis aeruginosa. However it was later found other cyanobacterial genera also produced them. There are about 60 known variants of microcystin, and several of these can be produced during a bloom. The most reported variant is microcystin-LR, possible because the earliest commercially available chemical standard analysis was for microcystin-LR.

Blooms containing microcystin are a problem worldwide in freshwater ecosystems. Microcystins are cyclic peptides and can be very toxic for plants and animals including humans. They bioaccumulate in the liver

Liver

The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...

of fish, in the hepatopancreas

Hepatopancreas

The hepatopancreas, digestive gland or midgut gland is an organ of the digestive tract of arthropods, molluscs and fish. It provides the functions which in mammals are provided separately by the liver and pancreas, including the production of digestive enzymes, and absorption of digested...

of mussels, and in zooplankton. They are hepatotoxic and can cause serious damage to the liver in humans. In this way they are similar to the nodularins (below), and together the microcystins and nodularins account for most of the toxic cyanobacterial blooms in fresh and brackish waters. In 2010, a number of sea otters were reported as having been poisoned by microcystin. Marine bivalves were the likely source of hepatotoxic shellfish poisoning

Shellfish poisoning

There are four syndromes called shellfish poisoning, which share some common features and are primarily associated with bivalve molluscs...

. This is the first confirmed example of mammals in a marine environment dying from ingesting a cyanotoxin.

Nodularins

The first nodularin variant to be identified was nodularin-R, produced by the cyanobacterium Nodularia spumigena
Nodularia
Nodularia is a genus of filamentous nitrogen-fixing cyanobacteria, or blue-green algae. They occur mainly in brackish or salinic waters, such as the hypersaline Makgadikgadi Pans, the Peel-Harvey Estuary in Western Australia or the Baltic Sea. Nodularia cells occasionally form heavy algal blooms...

. This cyanobacterium blooms in water bodies throughout the world. In the Baltic Sea

Baltic Sea

The Baltic Sea is a brackish mediterranean sea located in Northern Europe, from 53°N to 66°N latitude and from 20°E to 26°E longitude. It is bounded by the Scandinavian Peninsula, the mainland of Europe, and the Danish islands. It drains into the Kattegat by way of the Øresund, the Great Belt and...

, marine blooms of Nodularia spumigena are among some of the largest cyanobacterial mass events in the world.

Globally, the most common toxins present in cyanobacterial blooms in fresh and brackish waters are the cyclic peptide toxins of the nodularin family. Like the microcystin family (above), nodularins are potent hepatotoxins and can cause serious damage to the liver. They present health risks for wild and domestic animals as well as humans, and in many areas pose major challenges for the provision of safe drinking water.

Alkaloids

Alkaloid

Alkaloids are a group of naturally occurring chemical compounds that contain mostly basic nitrogen atoms. This group also includes some related compounds with neutral and even weakly acidic properties. Also some synthetic compounds of similar structure are attributed to alkaloids...

s are a group of naturally occurring chemical compound

Chemical compound

A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

s which mostly contain basic

Base (chemistry)

For the term in genetics, see base A base in chemistry is a substance that can accept hydrogen ions or more generally, donate electron pairs. A soluble base is referred to as an alkali if it contains and releases hydroxide ions quantitatively...

nitrogen

Nitrogen

Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

atoms. They are produced by a large variety of organisms, including cyanobacteria, and are part of the group of natural product

Natural product

A natural product is a chemical compound or substance produced by a living organism - found in nature that usually has a pharmacological or biological activity for use in pharmaceutical drug discovery and drug design...

s, also called secondary metabolite

Secondary metabolite

Secondary metabolites are organic compounds that are not directly involved in the normal growth, development, or reproduction of an organism. Unlike primary metabolites, absence of secondary metabolities does not result in immediate death, but rather in long-term impairment of the organism's...

s. Alkaloids act on diverse metabolic systems in humans and other animals, often with psychotropic or toxic effects. Almost uniformly, they are bitter tasting.

Anatoxin-a

Investigations into anatoxin-a

Anatoxin-a

Anatoxin-a, also known as Very Fast Death Factor, is a secondary, bicyclic amine alkaloid and cyanotoxin with acute neurotoxicity. The toxin is produced by at least four different genera of cyanobacteria and has been reported in North America, Europe, Africa, Asia, and New Zealand. The toxin is...

, also known as "Very Fast Death Factor", began in 1961 following the deaths of cows that drank from a lake containing an algal bloom in Saskatchewan, Canada. The toxin is produced by at least four different genera of cyanobacteria and has been reported in North America, Europe, Africa, Asia, and New Zealand.

Toxic effects from anatoxin-a progress very rapidly because it acts directly on the nerve cells (neuron

Neuron

A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...

s) as a neurotoxin

Neurotoxin

A neurotoxin is a toxin that acts specifically on nerve cells , usually by interacting with membrane proteins such as ion channels. Some sources are more general, and define the effect of neurotoxins as occurring at nerve tissue...

. The progressive symptoms of anatoxin-a exposure are loss of coordination, twitching

Fasciculation

A fasciculation , or "muscle twitch", is a small, local, involuntary muscle contraction and relaxation visible under the skin arising from the spontaneous discharge of a bundle of skeletal muscle fibers...

, convulsions and rapid death by respiratory paralysis. The nerve tissues which communicate with muscles contain a receptor

Receptor (biochemistry)

In biochemistry, a receptor is a molecule found on the surface of a cell, which receives specific chemical signals from neighbouring cells or the wider environment within an organism...

called the nicotinic acetylcholine receptor

Nicotinic acetylcholine receptor

Nicotinic acetylcholine receptors, or nAChRs, are cholinergic receptors that form ligand-gated ion channels in the plasma membranes of certain neurons and on the postsynaptic side of the neuromuscular junction...

. Stimulation of these receptors causes a muscular contraction. The anatoxin-a molecule is shaped so it fits this receptor, and in this way it mimics the natural neurotransmitter

Neurotransmitter

Neurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse. Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to...

normally used by the receptor, acetylcholine

Acetylcholine

The chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system in many organisms including humans...

. Once it has triggered a contraction, anatoxin-a does not allow the neurons to return to their resting state, because it is not degraded by cholinesterase

Cholinesterase

In biochemistry, cholinesterase is a family of enzymes that catalyze the hydrolysis of the neurotransmitter acetylcholine into choline and acetic acid, a reaction necessary to allow a cholinergic neuron to return to its resting state after activation.-Types:...

which normally performs this function. As a result the muscle cells contract permanently, the communication between the brain and the muscles is disrupted and breathing stops.

When it was first discovered, the toxin was called the Very Fast Death Factor (VFDF) because when it was injected into the body cavity

Intraperitoneal injection

Intraperitoneal injection or IP injection is the injection of a substance into the peritoneum . IP injection is more often applied to animals than humans...

of mice it induced tremors, paralysis and death within a few minutes. In 1977, the structure of VFDF was determined as a secondary, bicyclic amine

Amine

Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines,...

alkaloid

Alkaloid

, and it was renamed anatoxin-a. Structurally, it is similar to cocaine. There is continued interest in anatoxin-a because of the dangers it presents to recreational and drinking waters, and because it is a particularly useful molecule for investigating acetylcholine receptors in the nervous system. The deadliness of the toxin means that it has a high military potential as a toxin weapon.

Cylindrospermopsins

Cylindrospermopsin

Cylindrospermopsin is a cyanotoxin produced by a variety of freshwater cyanobacteria. CYN is a polycyclic uracil derivative containing guanidino and sulfate groups. It is also zwitterionic, making it highly water soluble. CYN is toxic to liver and kidney tissue and is thought to inhibit protein...

(abbreviated to CYN or CYL) was first discovered after an outbreak of a mystery disease on Palm Island

Palm Island, Queensland

Palm Island is an Aboriginal community located on Great Palm Island, also called by the Aboriginal name "Bwgcolman", an island on the Great Barrier Reef in North Queensland, Australia The settlement is also known by a variety of other names including "the Mission", Palm Island Settlement or Palm...

in Australia. The outbreak was traced back to a bloom of Cylindrospermopsis raciborskii in the local drinking water supply, and the toxin was subsequently identified. Analysis of the toxin led to a proposed chemical structure

Chemical structure

A chemical structure includes molecular geometry, electronic structure and crystal structure of molecules. Molecular geometry refers to the spatial arrangement of atoms in a molecule and the chemical bonds that hold the atoms together. Molecular geometry can range from the very simple, such as...

in 1992, which was revised after synthesis

Chemical synthesis

In chemistry, chemical synthesis is purposeful execution of chemical reactions to get a product, or several products. This happens by physical and chemical manipulations usually involving one or more reactions...

was achieved in 2000. Several variants of cylindrospermopsin, both toxic and non-toxic, have been isolated or synthesised.

Cylindrospermopsin is toxic

Toxicity

Toxicity is the degree to which a substance can damage a living or non-living organisms. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell or an organ , such as the liver...

to liver

Liver

and kidney

Kidney

The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...

tissue and is thought to inhibit protein synthesis

Protein biosynthesis

Protein biosynthesis is the process in which cells build or manufacture proteins. The term is sometimes used to refer only to protein translation but more often it refers to a multi-step process, beginning with amino acid synthesis and transcription of nuclear DNA into messenger RNA, which is then...

and to covalently modify DNA

DNA

Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

and/or RNA

RNA

Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....

. There is concern about the way cylindrospermopsin bioaccumulates in freshwater organisms. Toxic blooms of genera which produce cylindrospermopsin are most commonly found in tropical, subtropical and arid zone water bodies, and have recently been found in Australia, Europe, Israel, Japan and the USA.

Saxitoxins

Saxitoxin

Saxitoxin is a neurotoxin naturally produced by certain species of marine dinoflagellates and cyanobacteria Saxitoxin (STX) is a neurotoxin naturally produced by certain species of marine dinoflagellates (Alexandrium sp., Gymnodinium sp., Pyrodinium sp.) and cyanobacteria Saxitoxin (STX) is a...

(STX) is one of the most potent natural neurotoxin

Neurotoxin

s known. The term saxitoxin originates from the species name of the butter clam (Saxidomus
Saxidomus
Saxidomus, common name "Washington clams", is a genus of large edible saltwater clams, marine bivalve mollusks in the family Veneridae, the venus clams.The species Saxidomus giganteus is known as the "butter clam"....

giganteus) whereby it was first recognized. Saxitoxin is produced by the cyanobacteria Anabaena
Anabaena
Anabaena is a genus of filamentous cyanobacteria that exists as plankton. It is known for its nitrogen fixing abilities, and they form symbiotic relationships with certain plants, such as the mosquito fern. They are one of four genera of cyanobacteria that produce neurotoxins, which are harmful to...

spp., some Aphanizomenon
Aphanizomenon
Aphanizomenon is an important genus of cyanobacteria that inhabits freshwater lakes and can cause choking blooms. Studies on the species Aphanizomenon flos-aquae have shown that it can regulate buoyancy through light-induced changes in turgor pressure...

spp., Cylindrospermopsis sp., Lyngbya
Lyngbya
Lyngbya is a genus of cyanobacteria, unicellular autotrophs that form the basis of the oceanic food chain.Lyngbya form long unbranching filaments inside a rigid mucilage sheath. Sheaths may form tangles or mats, intermixed with other phytoplankton species...

sp. and Planktothrix
Planktothrix
Planktothrix is a genus of filamentous blue-green algae. Type species of the genus Planktothrix is Planktothrix agardhii Anagnostidis & Komárek. The genus was scrutinized in 2002 by S. Suda . Before, some species of the taxon were grouped within the genus Oscillatoria.- Species :* Planktothrix...

sp.). Puffer fish and some marine dinoflagellate

Dinoflagellate

s also produce saxitoxin. Saxitoxins bioaccumulate in shellfish and certain finfish. Ingestion of saxitoxin, usually through shellfish contaminated by toxic algal blooms, can result in paralytic shellfish poisoning

Paralytic shellfish poisoning

Paralytic shellfish poisoning is one of the four recognized syndromes of shellfish poisoning, which share some common features and are primarily associated with bivalve mollusks . These shellfish are filter feeders and, therefore, accumulate toxins produced by microscopic algae, such as...

.

Saxitoxin has been used in molecular biology to establish the function of the sodium channel. It acts on the voltage-gated sodium channels of nerve cells, preventing normal cellular function and leading to paralysis. The blocking of neuronal sodium channels which occurs in paralytic shellfish poisoning produces a flaccid paralysis

Flaccid paralysis

Flaccid paralysis is a clinical manifestation characterized by weakness or paralysis and reduced muscle tone without other obvious cause .-Polio:...

that leaves its victim calm and conscious through the progression of symptoms. Death often occurs from respiratory failure

Respiratory failure

The term respiratory failure, in medicine, is used to describe inadequate gas exchange by the respiratory system, with the result that arterial oxygen and/or carbon dioxide levels cannot be maintained within their normal ranges. A drop in blood oxygenation is known as hypoxemia; a rise in arterial...

. Saxitoxin was originally isolated and described by the United States military, who assigned it the chemical weapon designation

Chemical weapon designation

Chemical, biological, and radiological warfare agents are sometimes assigned what is termed a military symbol. Military symbols evolved out of the First World War from the British in part for secrecy, and to simplify reference to chemicals by something other than a chemical name...

"TZ". Saxitoxin is listed in schedule 1 of the Chemical Weapons Convention

Chemical Weapons Convention

The Chemical Weapons Convention is an arms control agreement which outlaws the production, stockpiling and use of chemical weapons. Its full name is the Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on their Destruction...

. According to the book Spycraft, U-2

Lockheed U-2

The Lockheed U-2, nicknamed "Dragon Lady", is a single-engine, very high-altitude reconnaissance aircraft operated by the United States Air Force and previously flown by the Central Intelligence Agency . It provides day and night, very high-altitude , all-weather intelligence gathering...

spyplane pilots were provided with needles containing saxitoxin to be used for suicide in the event escape was impossible.

Lipopolysaccharides

Lipopolysaccharide

Lipopolysaccharides , also known as lipoglycans, are large molecules consisting of a lipid and a polysaccharide joined by a covalent bond; they are found in the outer membrane of Gram-negative bacteria, act as endotoxins and elicit strong immune responses in animals.-Functions:LPS is the major...

s are present in all cyanobacteria. Though not as potent as other cyanotoxins, some researchers have claimed that all lipopolysaccharides in cyanobacteria can irritate the skin, while other researchers doubt the toxic effects are that generalized.

External links

Cyanosite - A Webserver for Cyanobacterial Research, Purdue University.
Dangers of toxic algae Environment Canterbury Updated 31 October 2009. Retrieved 23 January 2011.

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