Editing Cyanotoxin

{{short description|Toxin produced by cyanobacteria}}
[[File:Cyanobacterial Scum.JPG|thumb|upright=1.4|right|Green scum produced by and containing cyanobacteria, washed up on a rock in California during an [[algal bloom]]]]

'''Cyanotoxins''' are [[toxin]]s produced by [[cyanobacteria]] (also known as blue-green algae). Cyanobacteria are found almost everywhere, but particularly in lakes and in the ocean where, under high concentration of phosphorus conditions, they [[exponential growth|reproduce exponentially]] to form [[Algal bloom|blooms]]. Blooming cyanobacteria can produce cyanotoxins in such concentrations that they can [[poison]] and even kill animals and humans. Cyanotoxins can also accumulate in other animals such as fish and [[shellfish]], and cause poisonings such as [[shellfish poisoning]].

Some of the most powerful natural poisons known are cyanotoxins. They include potent [[neurotoxins]], [[hepatotoxins]], [[cytotoxins]], and [[endotoxins]]. The ''cyano'' in the term cyanobacteria refers to its colour, not to its relation to [[cyanide]]s, though cyanobacteria can [[catabolize]] [[hydrogen cyanide]] during [[nitrogen fixation]].<ref>{{citation | last1=Panou | first1=Manthos | last2=Gkelis | first2=Spyros | title=Cyano-assassins: Widespread cyanogenic production from cyanobacteria | date=2020-01-06 | doi=10.1101/2020.01.04.894782}}</ref>

Exposure to cyanobacteria can result in gastro-intestinal and hayfever symptoms or [[pruritic]] skin rashes.<ref>{{cite journal |vauthors=Stewart I, Webb PM, Schluter PJ, Shaw GR | year = 2006 | title = Recreational and occupational field exposure to freshwater cyanobacteria – a review of anecdotal and case reports, epidemiological studies and the challenges for epidemiologic assessment | journal = Environmental Health | volume = 5 | issue = 1| page = 6 | doi = 10.1186/1476-069X-5-6 | pmid = 16563159 | pmc = 1513208 | doi-access = free }}</ref> Exposure to the cyanobacteria neurotoxin [[BMAA]] may be an environmental cause of neurodegenerative diseases such as [[amyotrophic lateral sclerosis]] (ALS), [[Parkinson's disease]], and [[Alzheimer's disease]].<ref name=Holtcamp>{{cite journal | author = Holtcamp, W. | year = 2012 | title = The emerging science of BMAA: do cyanobacteria contribute to neurodegenerative disease? | journal = Environmental Health Perspectives | volume = 120 | issue = 3 | doi = 10.1289/ehp.120-a110 | pmid=22382274 | pmc=3295368 | pages=a110–a116}}</ref>  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."<ref name=Dixitetal>{{cite journal |vauthors=Dixit A, Dhaked RK, Alam SI, Singh L | year = 2005 | title = Military potential of biological neurotoxins | journal = Toxin Reviews| volume = 24 | issue = 2| pages = 175–207 | doi = 10.1081/TXR-200057850 | s2cid = 85651107 }}</ref>

The first published report that blue-green algae or cyanobacteria could have lethal effects appeared in ''[[Nature (journal)|Nature]]'' in 1878. George Francis described the algal bloom he observed in the estuary of the [[Murray River]] 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.<ref>{{cite journal | author = Francis G | year = 1878 | title = Poisonous Australian Lake | journal = Nature | volume = 18 | issue = 444| pages = 11–12 | doi = 10.1038/018011d0 |bibcode = 1878Natur..18...11F | s2cid = 46276288 | url = https://zenodo.org/record/1429233 }}</ref> 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.<ref>[http://www.chm.bris.ac.uk/motm/antx/antx.htm Anatoxin] Neil Edwards, University of Sussex at Brighton. Updated 1 September 1999. Retrieved 19 January 2011.</ref> In 2010, for the first time, marine mammals were reported to have died from ingesting cyanotoxins.<ref name=Milleretal />

==Background==
[[File:Satellite image of cyanobacteria bloom in the Great Lakes.png|thumb|upright=1.4|right|Satellite image of cyanobacteria bloom in the [[Great Lakes]]]]
{{main|Cyanobacteria}}

[[Cyanobacteria]] are ecologically one of the most prolific groups of [[phototroph]]ic [[prokaryote]]s in both marine and freshwater habitats. Both the beneficial and detrimental aspects of cyanobacteria are of considerable significance. They are important [[primary producer]]s as well as an immense source of several secondary products, including an array of toxic compounds known as cyanotoxins. Abundant growth of cyanobacteria in freshwater, [[estuarine]], and [[coastal ecosystem]]s due to increased anthropogenic [[eutrophication]] and global climate change has created serious concern toward harmful bloom formation and surface water contamination.<ref name=Rastogi2015 />

Cyanobacteria are considered the oldest groups of [[photosynthetic]] prokaryotes{{hsp}}<ref>{{cite journal |doi = 10.3389/fmicb.2014.00359|doi-access = free|title = Physiology and molecular biology of aquatic cyanobacteria|year = 2014|last1 = Bullerjahn|first1 = George S.|last2 = Post|first2 = Anton F.|journal = Frontiers in Microbiology|volume = 5|page = 359|pmid = 25076944|pmc = 4099938}}</ref> and possibly appeared on the Earth about 3.5 billion years ago.<ref>{{cite journal |doi = 10.1073/pnas.0600999103|title = The evolutionary diversification of cyanobacteria: Molecular-phylogenetic and paleontological perspectives|year = 2006|last1 = Tomitani|first1 = A.|last2 = Knoll|first2 = A. H.|last3 = Cavanaugh|first3 = C. M.|last4 = Ohno|first4 = T.|journal = Proceedings of the National Academy of Sciences|volume = 103|issue = 14|pages = 5442–5447|pmid = 16569695|pmc = 1459374|bibcode = 2006PNAS..103.5442T|doi-access = free}}</ref> They are ubiquitous in nature and thrive in a variety of ecological niches ranging from desert to hot springs and ice-cold water. Cyanobacteria are an immense source of several secondary natural products with applications in the food, pharmaceuticals, cosmetics, agriculture, and energy sectors.<ref>{{cite journal |doi = 10.1016/j.biotechadv.2009.04.009|title = Biotechnological and industrial significance of cyanobacterial secondary metabolites|year = 2009|last1 = Rastogi|first1 = Rajesh P.|last2 = Sinha|first2 = Rajeshwar P.|journal = Biotechnology Advances|volume = 27|issue = 4|pages = 521–539|pmid = 19393308}}</ref> Moreover, some species of cyanobacteria grow vigorously and form a dominant microflora in terms of their biomass and productivity in specific ecosystems. Bloom formations due to excessive growth of certain cyanobacteria followed by the production of toxic compounds have been reported in many [[eutrophic]] to [[hypertrophic]] lakes, ponds, and rivers throughout the world.<ref name=Rastogi2014>{{cite journal |doi = 10.1007/s11157-014-9334-6|title = The cyanotoxin-microcystins: Current overview|year = 2014|last1 = Rastogi|first1 = Rajesh P.|last2 = Sinha|first2 = Rajeshwar P.|last3 = Incharoensakdi|first3 = Aran|journal = Reviews in Environmental Science and Bio/Technology|volume = 13|issue = 2|pages = 215–249|s2cid = 84452003}}</ref><ref name=Rastogi2015 />

A range of toxic [[secondary compound]]s, called cyanotoxins, have been reported from cyanobacteria inhabiting freshwater and marine ecosystems. These toxic compounds are highly detrimental for survival of several aquatic organisms, wild and/or domestic animals, and humans. Aquatic organisms, including plants and animals, as well as [[phytoplankton]] and [[zooplankton]] inhabiting under toxic bloom rich ecosystems, are directly exposed to the harmful effects of different cyanotoxins. The intoxication occurring in wild and/or domestic animals and humans is either due to direct ingestion of cells of toxin producing cyanobacteria or the consumption of drinking water contaminated with cyanotoxins.<ref name=Rastogi2014 /> The toxicity of different cyanotoxins is directly proportional to the growth of cyanobacteria and the extent of their toxin production. It has been shown that the growth of different cyanobacteria and their toxin biosynthesis is greatly influenced by different abiotic factors such as light intensity, temperature, short wavelength radiations, pH, and nutrients.<ref name=Neilan2013>{{cite journal |doi = 10.1111/j.1462-2920.2012.02729.x|title = Environmental conditions that influence toxin biosynthesis in cyanobacteria|year = 2013|last1 = Neilan|first1 = Brett A.|last2 = Pearson|first2 = Leanne A.|last3 = Muenchhoff|first3 = Julia|last4 = Moffitt|first4 = Michelle C.|last5 = Dittmann|first5 = Elke|journal = Environmental Microbiology|volume = 15|issue = 5|pages = 1239–1253|pmid = 22429476|doi-access = free}}</ref><ref>{{cite journal |doi = 10.1039/c3pp50418b|title = Productivity of aquatic primary producers under global climate change|year = 2014|last1 = Häder|first1 = Donat-P.|last2 = Villafañe|first2 = Virginia E.|last3 = Helbling|first3 = E. Walter|journal = Photochem. Photobiol. Sci.|volume = 13|issue = 10|pages = 1370–1392|pmid = 25191675|doi-access = free|hdl = 11336/24725|hdl-access = free}}</ref><ref name=Rastogi2014 /> Global warming and temperature gradients can significantly change species composition and favor blooms of toxic phytoplanktons.<ref name=ElShehawy2012>{{cite journal |doi = 10.1016/j.watres.2011.11.021|title = Global warming and hepatotoxin production by cyanobacteria: What can we learn from experiments?|year = 2012|last1 = El-Shehawy|first1 = Rehab|last2 = Gorokhova|first2 = Elena|last3 = Fernández-Piñas|first3 = Francisca|last4 = Del Campo|first4 = Francisca F.|journal = Water Research|volume = 46|issue = 5|pages = 1420–1429|pmid = 22178305| bibcode=2012WatRe..46.1420E }}</ref><ref>{{cite journal |doi = 10.3389/fenvs.2015.00014|doi-access = free|title = Interactions of anthropogenic stress factors on marine phytoplankton|year = 2015|last1 = Hã¤Der|first1 = Donat-P.|last2 = Gao|first2 = Kunshan|journal = Frontiers in Environmental Science|volume = 3}}</ref><ref name=Rastogi2015 />

It has been assumed that cyanotoxins play an important role in [[chemical defense]] mechanisms giving survival advantages to the cyanobacteria over other microbes or deterring predation by higher [[trophic level]]s.<ref>{{cite journal |doi = 10.1016/j.toxicon.2006.11.017|title = Reciprocal allelopathic responses between toxic cyanobacteria (Microcystis aeruginosa) and duckweed (Lemna japonica)|year = 2007|last1 = Jang|first1 = Min-Ho|last2 = Ha|first2 = Kyong|last3 = Takamura|first3 = Noriko|journal = Toxicon|volume = 49|issue = 5|pages = 727–733|pmid = 17207510}}</ref><ref>{{cite journal |doi = 10.3390/md20080007|doi-access = free|title = Cyanobacterial Toxins as Allelochemicals with Potential Applications as Algaecides, Herbicides and Insecticides|year = 2008|last1 = Berry|first1 = John P.|last2 = Gantar|first2 = M.|last3 = Perez|first3 = M. H.|last4 = Berry|first4 = G.|last5 = Noriega|first5 = F. G.|journal = Marine Drugs|volume = 6|issue = 2|pages = 117–146|pmid = 18728763|pmc = 2525484}}</ref> Cyanotoxins may also take part in [[Cell signalling|chemical signalling]].<ref name=Rastogi2015 />

Cyanotoxins are produced by [[cyanobacteria]], a [[phylum (biology)|phylum]] of [[bacteria]] that obtain their energy through [[photosynthesis]]. The prefix ''[[cyan]]'' comes from the [[Greek language|Greek]] {{lang|grc|κύανoς}} meaning "a dark blue substance",<ref>[https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dku%2Fanos κύανος], Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', on Perseus</ref> 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;<ref name="IntroBot">{{cite book|last=Nabors|first=Murray W.|year=2004|title=Introduction to Botany|publisher=Pearson Education, Inc|location=San Francisco, CA|isbn=978-0-8053-4416-5}}</ref> they are now considered to be more closely related to bacteria,<ref>Ed. Guiry, M.D., John, D.M., Rindi, F and McCarthy, T.K. 2007. ''New Survey of Clare Island Volume 6: The Freshwater and Terrestrial Algae.'' Royal Irish Academy. {{ISBN|978-1-904890-31-7}}</ref> and the term for true ''[[algae]]'' is restricted to [[Eukaryote|eukaryotic]] organisms.<ref name="Allaby 92">{{cite encyclopedia|veditors = Allaby M|year=1992|encyclopedia=The Concise Dictionary of Botany|publisher=Oxford University Press|location=Oxford|title=Algae}}</ref> Like true algae, cyanobacteria are [[photosynthesize|photosynthetic]] and contain [[photosynthetic pigment]]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,<ref>Skulberg OM (1996) "Terrestrial and limnic algae and cyanobacteria". In: ''A Catalogue of Svalvard Plants, Fungi, Algae and Cyanobacteria'', Part 9, A Elvebakk and P Prestud (eds.) Norsk Polarinstitutt Skrifter, '''198''': 383-395.</ref> hotsprings<ref>{{cite book |last=Castenholz |first=R. A. |year=1973 |chapter=Ecology of blue-green algae in hotsprings |title=The Biology of Blue-green algae |editor-first=N. G. |editor-last=Carr |editor2-first=B. A. |editor2-last=Whitton |pages=379–414 |publisher=Blackwell |location=Oxford |isbn=0-632-09040-5 }}</ref> and [[wastewater]] treatment plants.<ref>{{cite journal |vauthors=Vasconcelos VM, Pereira E | year = 2001 | title = Cyanobacteria diversity and toxicity in a Wastewater Treatment Plant (Portugal) | journal = Water Research | volume = 35 | issue = 5| pages = 1354–1357 | doi = 10.1016/S0043-1354(00)00512-1 | pmid = 11268858 | bibcode = 2001WatRe..35.1354V }}</ref> They even inhabit the fur of polar bears, to which they impart a greenish tinge.<ref name="Karp G (2009)">{{cite book|author=Gerald Karp|title=Cell and Molecular Biology: Concepts and Experiments|url=https://books.google.com/books?id=arRGYE0GxRQC&pg=PA14|access-date=26 January 2011|date=19 October 2009|publisher=John Wiley and Sons|isbn=978-0-470-48337-4|pages=14–}}</ref> Cyanobacteria produce potent toxins, but they also produce helpful [[Bioactive compound|bioactive]] compounds, including substances with antitumour, antiviral, anticancer, antibiotic and antifungal activity, UV protectants and specific [[enzyme inhibitor|inhibitors of enzymes]].<ref name="Herrero">{{Cite book |last1=Herrero |first1=Antonia |title=The Cyanobacteria: Molecular Biology, Genomics and Evolution |last2=Flores |first2=Enrique |publisher=Caister Academic Press |year=2008 |isbn=978-1-904455-15-8}}</ref><ref name="Sivonen&Jones" />

==Harmful algal blooms==
{{further|Algal bloom|Eutrophication}}
[[File:Formation of cyanobacterial blooms.jpg|thumb|upright=2| {{center|'''Formation of cyanobacterial blooms'''}} Key factors include [[Human impact on the environment|anthropogenic]] [[eutrophication]], global climate change such as increased temperature and light or global warming due to an increase in ozone depleting substances (e.g., CO<sub>2</sub>, N<sub>2</sub>O, etc.), and other [[biotic factor|biotic]] and [[abiotic factor]]s responsible for the worldwide bloom incidence.<ref name=Rastogi2015>{{cite journal |doi = 10.3389/fmicb.2015.01254|doi-access = free|title = Bloom Dynamics of Cyanobacteria and Their Toxins: Environmental Health Impacts and Mitigation Strategies|year = 2015|last1 = Rastogi|first1 = Rajesh P.|last2 = Madamwar|first2 = Datta|last3 = Incharoensakdi|first3 = Aran|journal = Frontiers in Microbiology|volume = 6|page = 1254|pmid = 26635737|pmc = 4646972}} [[File:CC-BY icon.svg|50px]] Material was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License].</ref>]]

Cyanotoxins are often implicated in what are commonly called ''[[red tide]]s'' or ''harmful algal blooms''. Lakes and oceans contain many single-celled organisms called [[phytoplankton]]. Under certain conditions, particularly when nutrient concentrations are high, these organisms [[exponential growth|reproduce exponentially]]. The resulting dense swarm of phytoplankton is called an [[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.<ref>Lindsey R and Scott M (2010) [http://earthobservatory.nasa.gov/Features/Phytoplankton/page1.php What are phytoplankton] [[NASA Earth Observatory]].</ref><ref name=NOAA_HAB>[http://www.glerl.noaa.gov/res/Centers/HABS/faqs.html Harmful algal blooms event response] {{Webarchive|url=https://web.archive.org/web/20160304193209/http://www.glerl.noaa.gov/res/Centers/HABS/faqs.html |date=2016-03-04 }} [[NOAA]], Center of Excellence for Great Lakes and Human Health. Accessed 6 August 2014.</ref>

While some of these blooms are harmless, others fall into the category of [[harmful algal bloom]]s, or HABs. HABs can contain toxins or pathogens which result in [[fish kill]] and can also be fatal to humans.<ref name=NOAA_HAB /> In marine environments, HABs are mostly caused by [[dinoflagellate]]s,<ref name="Stewart&Falconer">Stewart I and Falconer IR (2008) [https://books.google.com/books?id=c6J5hlcjFaAC&dq=%22Cyanobacteria+and+cyanobacterial+toxins%22&pg=PA271 "Cyanobacteria and cyanobacterial toxins"] Pages 271–296 in ''Oceans and human health: risks and remedies from the seas'', Eds: Walsh PJ, Smith SL and Fleming LE. Academic Press, {{ISBN|0-12-372584-4}}.</ref> though species of other algae taxa can also cause HABs ([[diatom]]s, [[flagellate]]s, [[haptophyte]]s and [[raphidophyte]]s).<ref>Moestrup Ø, Akselman R, Cronberg G, Elbraechter M, Fraga S, Halim Y, Hansen G, Hoppenrath M, Larsen J, Lundholm N, Nguyen LN and Zingone A. [http://www.marinespecies.org/hab/ "IOC-UNESCO Taxonomic Reference List of Harmful Micro Algae (HABs)"]  Accessed 21 January 2011.</ref> 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.<ref name=Vasconcelos />

In freshwater ecosystems, algal blooms are most commonly caused by high levels of nutrients ([[eutrophication]]). The 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 smell bad when the cyanobacteria in the bloom die.<ref name=NOAA_HAB />

Strong cyanobacterial blooms reduce visibility to one or two centimetres. Species which are not reliant on sight (such as 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]]. 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.<ref name=Vasconcelos>{{cite journal | author = Vasconcelos V | year = 2006 | title = Eutrophication, toxic cyanobacteria and cyanotoxins: when ecosystems cry for help | url = http://www.limnetica.net/Limnetica/limne25a/L25a425_Eutrophication_toxic_cyanobacteria_cyanotoxins.pdf | journal = Limnetica | volume = 25 | issue = 1–2 | pages = 425–432 | doi = 10.23818/limn.25.30 | s2cid = 59434407 | access-date = 2011-01-26 | archive-url = https://web.archive.org/web/20110723182418/http://www.limnetica.net/Limnetica/limne25a/L25a425_Eutrophication_toxic_cyanobacteria_cyanotoxins.pdf | archive-date = 2011-07-23 | url-status = dead }}</ref>

In 1991 a harmful cyanobacterial bloom affected 1,000&nbsp;km of the [[Darling River|Darling]]-[[Barwon River (New South Wales)|Barwon River]] in Australia<ref name=Force1992>{{cite journal
 | author = Forc, N.S.W.B.G.A.T.
 | year = 1992
 | title = Final report of the NSW Blue-Green Algae Task Force
 | journal = Parramatta: NSW Department of Water Resources
}}</ref> at an economic cost of $10M AUD.<ref name=Herath1995>{{cite journal
 | author = Herath, G.
 | year = 1995
 | title = The algal bloom problem in Australian waterways: an economic appraisal
 | journal = Review of Marketing and Agricultural Economics
 | volume = 63
 | issue = 1
 | pages = 77–86
}}</ref>

==Chemical structure==
Cyanotoxins usually target the nervous system ([[neurotoxin]]s), the liver ([[hepatotoxin]]s) or the skin ([[dermatoxin]]s).<ref name="Sivonen&Jones" /> The chemical structure of cyanotoxins falls into three broad groups: cyclic peptides, alkaloids 
and lipopolysaccharides (endotoxins).<ref name="Chorus&Bartram" />

{| class="wikitable"
|+ Chemical structure of cyanotoxins<ref name="Chorus&Bartram" /> 
|-
! Structure
! Cyanotoxin
! Primary target organ in mammals 
! Cyanobacteria genera
|-
! rowspan="2" | [[Cyclic peptide]]s
| [[Microcystin]]s
| Liver
| ''[[Microcystis]]'', ''[[Anabaena]]'', ''[[Planktothrix]]'' (Oscillatoria), ''[[Nostoc]]'', ''[[Hapalosiphon]]'', ''[[Anabaenopsis]]'' 
|-
| [[Nodularin]]s
| Liver
| ''[[Nodularia]]''
|-
! rowspan="6" | [[Alkaloid]]s
| [[Anatoxin-a]]
| Nerve synapse 
| ''[[Anabaena]]'', ''[[Planktothrix]]'' (Oscillatoria), ''[[Aphanizomenon]]'' 
|-
| [[Guanitoxin]] 
| Nerve synapse
| ''[[Anabaena]]''
|-
| [[Cylindrospermopsin]]s
| Liver 
| ''[[Cylindrospermopsis]]'', ''[[Aphanizomenon]]'', ''[[Umezakia]]'' 
|-
| [[Lyngbyatoxin-a]]
| Skin, gastro-intestinal tract
| ''[[Lyngbya]]'' 
|-
| [[Saxitoxin]]
| Nerve synapse
| ''[[Anabaena]]'', ''[[Aphanizomenon]]'', ''[[Lyngbya]]'', ''[[Cylindrospermopsis]]'' 
|-
| [[Aetokthonotoxin]]
| white matter of the brain; toxicity to mammals not yet confirmed
| ''[[Aetokthonos]]'' 
|-
! rowspan="1" | [[Lipopolysaccharide]]s
| 
| Potential irritant; affects any exposed tissue
| All 
|-
! [[Polyketide]]s
| [[Aplysiatoxin]]s
| Skin
| ''[[Lyngbya]]'', ''[[Schizothrix]]'', ''[[Planktothrix]]'' (Oscillatoria)
|-
! [[Amino acid|Amino Acid]]
| [[BMAA]]
| [[Nervous system]]
| All
|}
 
Most cyanotoxins have a number of variants ([[chemical analog|analogues]]). As of 1999, altogether over 84 cyanotoxins were known and only a small number have been well studied.<ref name="Sivonen&Jones">Sivonen K and Jones G (1999) [https://www.who.int/water_sanitation_health/resourcesquality/toxicyanbact/en/ "Cyanobacterial Toxins"] {{webarchive|url=https://web.archive.org/web/20070124215138/http://www.who.int/water_sanitation_health/resourcesquality/toxicyanbact/en/ |date=2007-01-24 }} In ''Toxic Cyanobacteria in Water.'' Chorus I and Bartram J (eds): 41-111. WHO, Geneva. {{ISBN|0419239308}}.</ref>

==Cyclic peptides==
A [[peptide]] is a short [[polymer]] of [[amino acid]]s linked by [[peptide bond]]s. They have the same chemical structure as [[protein]]s, except they are shorter. In a [[cyclic peptide]], the ends link 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.<ref name="Chorus&Bartram" />

===Microcystins===
[[File:Microcystin-LR.svg|thumb|[[Microcystin LR]]]]

As with other cyanotoxins, [[microcystin]]s were named after the first organism discovered to produce them, ''Microcystis aeruginosa''. However it was later found other cyanobacterial genera also produced them.<ref name="Chorus&Bartram" /> 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]], possibly because the earliest commercially available chemical standard analysis was for microcystin-''LR''.<ref name="Chorus&Bartram">{{Cite book |last1=Chorus |first1=Ingrid |url=https://www.taylorfrancis.com/books/9781003081449 |title=Toxic Cyanobacteria in Water: A Guide to Their Public Health Consequences, Monitoring and Management |last2=Welker |first2=Martin |date=2021-03-07 |publisher=CRC Press |isbn=978-1-003-08144-9 |edition=2 |location=London |language=en |doi=10.1201/9781003081449}}</ref>

Blooms containing microcystin are a problem worldwide in freshwater ecosystems.<ref name="PelaezAntoniou2010">{{Cite book|last1=Pelaez|first1=Miguel|title=Xenobiotics in the Urban Water Cycle|last2=Antoniou|first2=Maria G.|last3=He|first3=Xuexiang|last4=Dionysiou|first4=Dionysios D.|last5=de la Cruz|first5=Armah A.|last6=Tsimeli|first6=Katerina|last7=Triantis|first7=Theodoros|last8=Hiskia|first8=Anastasia|last9=Kaloudis|first9=Triantafyllos|last10=Williams|first10=Christopher|last11=Aubel|first11=Mark|last12=Chapman|first12=Andrew|last13=Foss|first13=Amanda|last14=Khan|first14=Urooj|last15=O’Shea|first15=Kevin E.|last16=Westrick|first16=Judy|chapter=Sources and Occurrence of Cyanotoxins Worldwide |display-authors=6|volume=16|year=2010|pages=101–127|issn=1566-0745|doi=10.1007/978-90-481-3509-7_6|series=Environmental Pollution|isbn=978-90-481-3508-0}}</ref> Microcystins are cyclic peptides and can be very toxic for plants and animals including humans. They bioaccumulate in the [[liver]] of fish, in the [[hepatopancreas]] of mussels, and in zooplankton. They are [[hepatotoxic]] and can cause serious damage to the liver in humans.<ref name="Chorus&Bartram" /> 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.<ref name="Sivonen&Jones" /> In 2010, a number of [[sea otter]]s were poisoned by microcystin. Marine [[bivalve]]s were the likely source of hepatotoxic [[shellfish poisoning]]. This was the first confirmed example of a marine mammal dying from ingesting a cyanotoxin.<ref name=Milleretal>{{cite journal  |vauthors=Miller MA, Kudela RM, Mekebri A, Crane D, Oates SC, etal | year = 2010 | title = Evidence for a Novel Marine Harmful Algal Bloom: Cyanotoxin (Microcystin) Transfer from Land to Sea Otters | journal = PLOS ONE | volume = 5 | issue = 9| page = e12576 | doi = 10.1371/journal.pone.0012576 | editor1-last = Thompson | editor1-first = Ross | pmid=20844747 | pmc=2936937|bibcode = 2010PLoSO...512576M | doi-access = free }}</ref>

{{clear}}

===Nodularins===
[[File:Nodularin R.svg|thumb|[[Nodularin-R]]]]

The first nodularin variant to be identified was [[nodularin-R]], produced by the cyanobacterium ''[[Nodularia|Nodularia spumigena]]''.<ref>{{cite journal |vauthors=Sivonen K, Kononen K, Carmichael WW, Dahlem AM, Rinehart KL, Kiviranta J, Niemela SI |title=Occurrence of the hepatotoxic cyanobacterium Nodularia spumigena in the Baltic Sea and structure of the toxin |journal=Appl. Environ. Microbiol. |volume=55 |issue=8 |pages=1990–5 |year=1989 |doi=10.1128/aem.55.8.1990-1995.1989 |pmid=2506812 |pmc=202992|bibcode=1989ApEnM..55.1990S }}</ref> This cyanobacterium blooms in water bodies throughout the world. In the [[Baltic Sea]], marine blooms of ''Nodularia spumigena'' are among some of the largest cyanobacterial mass events in the world.<ref>{{cite journal |author1=David P. Fewer DP |author2=Köykkä K |author3=Halinen K |author4=Jokela J |author5=Lyra C |author6=Sivonen K | year = 2009 | title = Culture-independent evidence for the persistent presence and genetic diversity of microcystin-producing Anabaena (Cyanobacteria) in the Gulf of Finland | journal = Environmental Microbiology | volume = 11 | issue = 4| pages = 855–866 | doi = 10.1111/j.1462-2920.2008.01806.x | pmid = 19128321 }}</ref> (Parts of nine industrialized countries drain into the Baltic Sea, which has little water exchange with the North Sea and Atlantic Ocean. It is consequently one of the more polluted bodies of water in the world (nutrient-rich, from the perspective of cyanobacteria).)

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.<ref name="Sivonen&Jones" />

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==Alkaloids==
[[Alkaloid]]s are a group of naturally occurring [[chemical compound]]s which mostly contain [[base (chemistry)|basic]] [[nitrogen]] atoms. They are produced by a large variety of organisms, including cyanobacteria, and are part of the group of [[natural product]]s, also called [[secondary metabolite]]s. Alkaloids act on diverse metabolic systems in humans and other animals, often with [[psychotropic]] or toxic effects. Almost uniformly, they are [[Bitter (taste)#Bitterness|bitter tasting]].<ref name=Rhoades1979>{{cite book|year=1979 |author=Rhoades, David F |chapter=Evolution of Plant Chemical Defense against Herbivores |editor1=Rosenthal, Gerald A. |editor2=Janzen, Daniel H |title=Herbivores: Their Interaction with Secondary Plant Metabolites |place=New York |publisher=Academic Press |page=41 |isbn=978-0-12-597180-5}}</ref>

===Anatoxin-''a''===
[[File:Anatoxin-a.png|thumb|140px|right|[[Anatoxin-a|Anatoxin-''a'']]]]

Investigations into [[Anatoxin-a|anatoxin-''a'']], 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.<ref>{{cite journal |vauthors=Carmichael WW, Gorham PR | year = 1978 | title = Anatoxins from clones of Anabaena flos-aquae isolated from lakes of western Canada | journal = Mitt. Infernal. Verein. Limnol | volume = 21 | pages = 285–295 }}</ref><ref>{{cite journal |vauthors=Carmichael WW, Biggs DF, Gorham PR | year = 1975 | title = Toxicology and pharmacological action of Anabaena flos-aquae toxin | journal = Science | volume = 187 | issue = 4176| pages = 542–544 | doi = 10.1126/science.803708 | pmid = 803708 |bibcode = 1975Sci...187..542C }}</ref> 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.<ref>Yang, X (2007) ''[https://www.proquest.com/dissertations-theses/occurrence-cyanobacterial-neurotoxin-anatoxin-new/docview/304810666/se-2 Occurrence of the cyanobacterial neurotoxin, anatoxin-a, in New York State waters]'' ProQuest Dissertations and Theses. {{ISBN|978-0-549-35451-2}}.</ref>

Toxic effects from anatoxin-''a'' progress very rapidly because it acts directly on the nerve cells ([[neuron]]s) as a [[neurotoxin]]. The progressive symptoms of anatoxin-''a'' exposure are loss of coordination, [[Fasciculation|twitching]], convulsions and rapid death by [[respiratory paralysis]]. The nerve tissues which communicate with muscles contain a [[Receptor (biochemistry)|receptor]] called the [[nicotinic acetylcholine receptor]]. 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]] normally used by the receptor, [[acetylcholine]]. 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]] 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.<ref>{{cite journal |author1=Wood S. A. |author2=Rasmussen J. P. |author3=Holland P. T. |author4=Campbell R. |author5=Crowe A. L. M. | year = 2007 | title = First Report of the Cyanotoxin Anatoxin-A from Aphanizomenon issatschenkoi (cyanobacteria) | journal = Journal of Phycology | volume = 43 | issue = 2| pages = 356–365 | doi = 10.1111/j.1529-8817.2007.00318.x |s2cid=84284928 }}</ref><ref>National Center for Environmental Assessment. "Toxicological Reviews of Cyanobacterial Toxins: Anatoxin-a" NCEA-C-1743</ref>
{{External media
 |float=left
 |width=210px
 |video1=[http://www.periodicvideos.com/videos/mv_veryfastdeathfactor.htm Very Fast Death Factor]<br />University of Nottingham
}}
The toxin was called the Very Fast Death Factor because it induced tremors, paralysis and death within a few minutes when [[Intraperitoneal injection|injected into the body cavity]] of mice. In 1977, the structure of VFDF was determined as a secondary, bicyclic [[amine]] [[alkaloid]], and it was renamed anatoxin-''a''.<ref>{{cite journal | vauthors = Devlin JP, Edwards OE, Gorham PR, Hunter NR, Pike RK, Stavric B | year = 1977 | title = Anatoxin-a, a toxic alkaloid from Anabaena flos-aquae NRC-44h | journal = Can. J. Chem. | volume = 55 | issue = 8 | pages = 1367–1371 | doi = 10.1139/v77-189 | doi-access = free }}</ref><ref>{{cite journal | author = Moore RE | year = 1977 | title = Toxins from blue-green algae | journal = BioScience | volume = 27 | issue = 12| pages = 797–802 | jstor = 1297756 | doi = 10.2307/1297756  }}</ref> Structurally, it is similar to [[cocaine]].<ref name=Metcalf>{{Cite journal | doi=10.3109/17482960903272942|title = Cyanobacteria, neurotoxins and water resources: Are there implications for human neurodegenerative disease?| journal=Amyotrophic Lateral Sclerosis| volume=10| pages=74–78|year = 2009|last1 = Metcalf|first1 = James S.| last2=Codd| first2=Geoffrey A.| pmid=19929737|s2cid = 41880444}}</ref> 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.<ref name=Stewartetal>{{Cite book |vauthors=Stewart I, Seawright AA, Shaw GR | title = Cyanobacterial Harmful Algal Blooms: State of the Science and Research Needs | year = 2008 | chapter = Cyanobacterial poisoning in livestock, wild mammals and birds – an overview |chapter-url=http://www.epa.gov/cyano_habs_symposium/monograph/Ch28.pdf |archive-url=https://web.archive.org/web/20131023060513/http://www.epa.gov/cyano_habs_symposium/monograph/Ch28.pdf |url-status=dead |archive-date=2013-10-23 | volume = 619 | pages = 613–637 | doi = 10.1007/978-0-387-75865-7_28 | pmid = 18461786 | series = Advances in Experimental Medicine and Biology | isbn = 978-0-387-75864-0 }}</ref> The deadliness of the toxin means that it has a high military potential as a toxin weapon.<ref name=Dixitetal />

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===Cylindrospermopsins===
[[File:Cylindrospermopsin.png|thumb|140px|right|[[Cylindrospermopsin]]]]

[[Cylindrospermopsin]] (abbreviated to CYN or CYL) was first discovered after an outbreak of a mystery disease on [[Palm Island, Queensland|Palm Island]] in Australia.<ref name=Byth1980>{{cite journal |author=Byth S |title=Palm Island mystery disease |journal=The Medical Journal of Australia |volume=2 |issue=1 |pages=40–42 |date=July 1980 |doi=10.5694/j.1326-5377.1980.tb131814.x |pmid=7432268|s2cid=273293 }}</ref> 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]] in 1992, which was revised after [[chemical synthesis|synthesis]] was achieved in 2000. Several variants of cylindrospermopsin, both toxic and non-toxic, have been isolated or synthesised.<ref>{{cite journal |vauthors=Griffiths DJ, Saker ML | year = 2003 | title = The Palm Island mystery disease 20 years on: a review of research on the cyanotoxin cylindrospermopsin | journal = Environ Toxicol | volume = 18 | issue = 2| pages = 78–93 | pmid = 12635096 | doi = 10.1002/tox.10103 | bibcode = 2003EnTox..18...78G | s2cid = 25219655 }}</ref>

Cylindrospermopsin is [[toxicity|toxic]] to [[liver]] and [[kidney]] tissue and is thought to inhibit [[Protein biosynthesis|protein synthesis]] and to [[covalent]]ly modify [[DNA]] and/or [[RNA]]. There is concern about the way cylindrospermopsin [[bioaccumulate]]s in freshwater organisms.<ref>{{cite journal | author = Kinnear S | year = 2010 | title = Cylindrospermopsin: A Decade of Progress on Bioaccumulation Research | journal = Marine Drugs | volume = 8 | issue = 3| pages = 542–564 | doi = 10.3390/md8030542 | pmid = 20411114 | pmc = 2857366 | doi-access = free }}</ref> 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.<ref name="Chorus&Bartram" />

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===Saxitoxins===
[[File:Saxitoxin.svg|thumb|140px|[[Saxitoxin]]]]

[[Saxitoxin]] (STX) is one of the most potent natural [[neurotoxin]]s known. The term saxitoxin originates from the species name of the butter clam (''[[Saxidomus]] giganteus'') whereby it was first recognized. Saxitoxin is produced by the cyanobacteria ''[[Anabaena]]'' spp., some ''[[Aphanizomenon]]'' spp., ''[[Cylindrospermopsis]]'' sp., ''[[Lyngbya]]'' sp. and ''[[Planktothrix]]'' sp., among others).<ref name="uhm">{{cite journal |vauthors=Clark RF, Williams SR, Nordt SP, Manoguerra AS |title=A review of selected seafood poisonings |journal=Undersea Hyperb Med |volume=26 |issue=3 |pages=175–84 |year=1999 |pmid=10485519 |url=http://archive.rubicon-foundation.org/2314 |access-date=2008-08-12 |archive-url=https://web.archive.org/web/20110811180444/http://archive.rubicon-foundation.org/2314 |archive-date=2011-08-11 |url-status=usurped }}</ref> [[Puffer fish]] and some marine [[dinoflagellate]]s also produce saxitoxin.<ref>{{cite journal |vauthors=Nakamuraa M, Oshimaa Y, Yasumoto T | year = 1984 | title = Occurrence of saxitoxin in puffer fish | journal = Toxicon | volume = 22 | issue = 3| pages = 381–385 | doi = 10.1016/0041-0101(84)90082-5 | pmid = 6474491 }}</ref><ref>{{cite journal | author = Landsberg JH | year = 2002 | title = The effects of harmful algal blooms on aquatic organisms | journal = Reviews in Fisheries Science | volume = 10 | issue = 2| pages = 113–390 | doi=10.1080/20026491051695| s2cid = 86185142 }}</ref> Saxitoxins bioaccumulate in shellfish and certain finfish. Ingestion of saxitoxin, usually through shellfish contaminated by toxic algal blooms, can result in [[paralytic shellfish poisoning]].<ref name="Sivonen&Jones" />

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]] that leaves its victim calm and conscious through the progression of symptoms. Death often occurs from [[respiratory failure]].<ref>Kao CY and Levinson SR (1986) ''Tetrodotoxin, saxitoxin, and the molecular biology of the sodium channel'' New York Academy of Sciences. {{ISBN|0-89766-354-3}}.</ref> Saxitoxin was originally isolated and described by the [[United States military]], who assigned it the [[chemical weapon designation]] "TZ". Saxitoxin is listed in [[List of Schedule 1 substances (CWC)|schedule 1]] of the [[Chemical Weapons Convention]].<ref>[http://www.opcw.org/chemical-weapons-convention/annex-on-chemicals/b-schedules-of-chemicals/schedule-1/ Chemical Weapons Convention: Schedule 1] {{webarchive|url=https://web.archive.org/web/20130607201658/http://www.opcw.org/chemical-weapons-convention/annex-on-chemicals/b-schedules-of-chemicals/schedule-1/ |date=2013-06-07 }} Organisation for the Prohibition of Chemical Weapons, The Hague, Netherlands. Retrieved 26 January 2011.</ref> According to the book ''Spycraft'', [[Lockheed U-2|U-2]] spyplane pilots were provided with needles containing saxitoxin to be used for suicide in the event escape was impossible.<ref>Wallace R, Melton HK and Schlesinger HR (2009) ''Spycraft: the secret history of the CIA's spytechs from communism to Al-Qaeda''. Penguin Group USA, {{ISBN|0-452-29547-5}}.</ref>

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===Aetokthonotoxin===
[[File:Toxin transmission from cyanobacteria to the bald eagle.jpg|thumb|upright=0.8| {{center|Transmission from cyanobacteria to the bald eagle}}]]

[[Aetokthonotoxin]] (abbreviated to AETX) was discovered in 2021 as the cyanobacterial neurotoxin causing [[Avian vacuolar myelinopathy|vacuolar myelinopathy]] (VM).<ref name=Breinlinger>{{Cite journal|last1=Breinlinger|first1=Steffen|last2=Phillips|first2=Tabitha J.|last3=Haram|first3=Brigette N.|last4=Mareš|first4=Jan|last5=Yerena|first5=José A. Martínez|last6=Hrouzek|first6=Pavel|last7=Sobotka|first7=Roman|last8=Henderson|first8=W. Matthew|last9=Schmieder|first9=Peter|last10=Williams|first10=Susan M.|last11=Lauderdale|first11=James D.|date=2021-03-26|title=Hunting the eagle killer: A cyanobacterial neurotoxin causes vacuolar myelinopathy|journal=Science|language=en|volume=371|issue=6536|pages=eaax9050|doi=10.1126/science.aax9050|issn=0036-8075|pmid=33766860|pmc=8318203|doi-access=free}}</ref> As the biosynthesis of aetokthonotoxin depends on the availability of bromide in freshwater systems and requires an interplay between the toxin-producing cyanobacterium ''[[Aetokthonos hydrillicola]]'' and the host plant it epiphytically grows on (most importantly [[hydrilla]]), it took > 25 years to discover aetokthonotoxin as the VM-inducing toxin after the disease has first been diagnosed in bald eagles in 1994.<ref name=USGS>{{cite web|title=Avian vacuolar myelinopathy|url=http://www.nwhc.usgs.gov/disease_information/avian_vacuolar_myelinopathy/|publisher=USGS National Wildlife Health Center|accessdate=24 October 2013|archive-url=https://web.archive.org/web/20141006080313/http://www.nwhc.usgs.gov/disease_information/avian_vacuolar_myelinopathy/|archive-date=6 October 2014|url-status=dead}}</ref> The toxin cascades through the food-chain: Among other animals, it affects fish and waterfowl such as [[coots]] or ducks which feed on [[hydrilla]] colonized with the cyanobacterium. Aetokthonotoxin is transmitted to raptors, such as the [[bald eagle]], that prey on these affected animals.<ref name=four>{{cite journal|last=Birrenkott|first=A. H.|author2=S. B Wilde |author3=J. J. Hains |author4=J. R. Fisher |author5=T. M. Murphy |author6=C. P. Hope |author7=P. G. Parnell |author8=W. W. Bowerman |title=Establishing a food-chain link between aquatic plant material and avian vacuolar myelinopathy in mallards (Anas platyrhynchos)|journal=Journal of Wildlife Diseases|year=2004|volume=40|issue=3|pages=485–492|doi=10.7589/0090-3558-40.3.485|pmid=15465716|doi-access=free}}</ref>

[[Avian vacuolar myelinopathy|Vacuolar myelinopathy]] is characterized by widespread vacuolization of the myelinated axons (intramyelinic edema) in the white matter of the brain and spinal cord. Clinical signs of the intoxication include the severe loss of motor functions and sight. Affected birds fly into objects, lack coordination in swimming, flying and walking, develop tremors of the head and lose their responsiveness. As the toxin has been shown to bioaccumulate, there is concern that it might also be a threat to human health.<ref name=Breinlinger /> However, toxicity to mammals has yet to be confirmed experimentally.

[[File:Aetokthonotoxin.png|thumb|140px|left|[[Aetokthonotoxin]]]]

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==Lipopolysaccharides==
[[Lipopolysaccharide]]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.<ref>{{cite journal |vauthors=Stewart I, Schluter PJ, Shaw GR |title=Cyanobacterial lipopolysaccharides and human health - a review |journal=Environ Health |volume=5 |issue= 1|pages=7 |year=2006 |pmid=16563160 |pmc=1489932 |doi=10.1186/1476-069X-5-7 |doi-access=free }}</ref>

==Amino acids==

===BMAA===
The non-proteinogenic amino acid [[beta-Methylamino-L-alanine]] (BMAA) is ubiquitously produced by cyanobacteria in marine, [[freshwater]], [[brackish]], and terrestrial environments.<ref name=Cox>{{cite journal |author1=Cox, PA |author2=Banack, SA |author3=Murch, SJ |author4=Rasmussen, U |author5=Tien, G |author6=Bidigare, RR |author7=Metcalf, JS |author8=Morrison, LF |author9=Codd, GA |author10=Bergman, B. | year = 2005 | title = Diverse taxa of cyanobacteria produce b-N-methylamino-L-alanine, a neurotoxic amino acid | journal = PNAS | volume = 102 | issue = 14 | doi = 10.1073/pnas.0501526102|bibcode = 2005PNAS..102.5074C | pmid=15809446 | pmc=555964 | pages=5074–5078|doi-access=free }}</ref><ref name=Esterhuizen>{{cite journal |author1=Esterhuizen, M |author2=Downing, TG. | year = 2008 | title = β-N-methylamino-L-alanine (BMAA) in novel South African cyanobacterial isolates | journal = Ecotoxicology and Environmental Safety | volume = 71 | issue = 2 | doi = 10.1016/j.ecoenv.2008.04.010 | pages=309–313 | pmid=18538391}}</ref>  The exact mechanisms of BMAA toxicity on neuron cells is being investigated.  Research suggests both acute and chronic mechanisms of toxicity.<ref name=Weiss>{{cite journal | vauthors = Weiss JH, Koh JY, Choi DW | year = 1989 | title = Neurotoxicity of β -N-methylamino-L-alanine (BMAA) and β-N-oxalylamino-L-alanine (BOAA) on cultured cortical neurons | journal = Brain Research | volume = 497 | issue = 1 | doi = 10.1016/0006-8993(89)90970-0 | pages=64–71 | pmid=2551452| s2cid = 140209787 }}</ref><ref name=Lobner>{{cite journal |author1=Lobner, D |author2=Piana, PM |author3=Salous, AK |author4=Peoples, RW. | year = 2007 | title = β-N-methylamino-L-alanine enhances neurotoxicity through multiple mechanisms | journal = Neurobiology of Disease | volume = 25 | issue = 2 | doi = 10.1016/j.nbd.2006.10.002 | pages=360–366 | pmid=17098435 | pmc=3959771}}</ref>  BMAA is being investigated as a potential environmental risk factor for neurodegenerative diseases, including [[ALS]], [[Parkinson's disease]] and [[Alzheimer's disease]].<ref name="Cox and Davis">{{cite journal | vauthors = Cox PA, Davis DA, Mash DC, Metcalf JS, Banack SA | year = 2015 | title = Dietary exposure to an environmental toxin triggers neurofibrillary tangles and amyloid deposits in the brain | journal = Proceedings of the Royal Society B | volume = 283 | issue = 1823 | doi = 10.1098/rspb.2015.2397 | pmid = 26791617 | pmc = 4795023 | pages=20152397}}</ref>

==Gallery==
Other cyanotoxins:
<gallery>
Image:Anatoxin-a-S.png|Guanitoxin
Image:Aplysiatoxin.svg|Aplysiatoxin
</gallery>

==See also==
* [[Dinotoxin]]
* [[Microbial mat]]s
* [[Microbial toxin]]s
* [[Microviridin]]

==References==
{{reflist|30em}}

==External links==
* [https://web.archive.org/web/20190622193335/http://www-cyanosite.bio.purdue.edu/index.html Cyanosite] - A Webserver for Cyanobacterial Research, Purdue University.
* [https://web.archive.org/web/20101215133500/http://ecan.govt.nz/services/online-services/monitoring/swimming-water-quality/Pages/toxic-algae.aspx Dangers of toxic algae] [[Environment Canterbury]] Updated 31 October 2009. Retrieved 23 January 2011.

{{Cyanotoxins}}
{{marine pollution}}
{{Authority control}}

[[Category:Cyanotoxins| ]]