Quizzes Lists Topics

Cyanotoxin

Cyanotoxins are toxins 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 to form blooms. Blooming cyanobacteria can produce cyanotoxins in such concentrations that they 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.

Among cyanotoxins are some of the most powerful natural poisons known, including poisons which can cause rapid death by respiratory failure.[1] The toxins include potent neurotoxins, hepatotoxins, cytotoxins, and endotoxins. Despite the similarity in name, they are not cyanides. Recreational exposure to cyanobacteria can result in gastro-intestinal and hay fever symptoms or pruritic skin rashes.[2] Exposure to the cyanobacteria neurotoxin BMAA may be an environmental cause of neurodegenerative diseases such as ALS, Parkinson's Disease and Alzheimer's Disease.[3] 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."[4]

The first published report that blue-green algae or cyanobacteria could have lethal effects appeared in 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.[5] 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.[6] In 2010, for the first time, marine mammals were reported to have died from ingesting cyanotoxins.[7]

Cyanobacteria

Cyanotoxins are produced by cyanobacteria, a phylum of bacteria that obtain their energy through photosynthesis. The prefix cyan comes from the Greek κύανoς meaning "a dark blue substance",[8] 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;[9] they are now considered to be more closely related to bacteria,[10] and the term for true algae is restricted to eukaryotic organisms.[11] Like true algae, cyanobacteria are photosynthetic and contain photosynthetic pigments, 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,[12] hotsprings[13] and wastewater treatment plants.[14] They even inhabit the fur of polar bears, to which they impart a greenish tinge.[15] 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.[16] [17]

Harmful algal blooms
Dense bloom of cyanobacteria on the Potomac River estuary. These blooms can be toxic.

Cyanotoxins are often implicated in what are commonly called red tides 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 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.[18] [19]

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 and can also be fatal to humans.[19] In marine environments, HABs are mostly caused by dinoflagellates,[20] though species of other algae taxa can also cause HABs (diatoms, flagellates, haptophytes and raphidophytes).[21] 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.[22]

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.[19]

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.[22]

In 1991 a harmful cyanobacterial bloom affected 1,000 km of the Darling-Barwon River in Australia[23] at an economic cost of $10M AUD.[24]

Chemical structure

Cyanotoxins usually target the nervous system (neurotoxins), the liver (hepatotoxins) or the skin (dermatoxins).[17] The chemical structure of cyanotoxins falls into three broad groups: cyclic peptides, alkaloids and lipopolysaccharides (endotoxins).[25]

Chemical structure of cyanotoxins[25]
Structure Cyanotoxin Primary target organ in mammals Cyanobacteria genera
Cyclic peptides Microcystins Liver Microcystis, Anabaena, Planktothrix (Oscillatoria), Nostoc, Hapalosiphon, Anabaenopsis
Nodularins Liver Nodularia
Alkaloids Anatoxin-a Nerve synapse Anabaena, Planktothrix (Oscillatoria), Aphanizomenon
Anatoxin-a(S) Nerve synapse Anabaena
Cylindrospermopsins Liver Cylindrospermopsis, Aphanizomenon, Umezakia
Lyngbyatoxin-a Skin, gastro-intestinal tract Lyngbya
Saxitoxin Nerve synapse Anabaena, Aphanizomenon, Lyngbya, Cylindrospermopsis
Lipopolysaccharides Potential irritant; affects any exposed tissue All
Polyketides Aplysiatoxins Skin Lyngbya, Schizothrix, Planktothrix (Oscillatoria)
Amino Acid BMAA Nervous System All

Most cyanotoxins have a number of variants (analogues). As of 1999, altogether over 84 cyanotoxins were known and only a small number have been well studied.[17]

Cyclic peptides

A peptide is a short polymer of amino acids linked by peptide bonds. They have the same chemical structure as proteins, 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.[25]

Microcystins

As with other cyanotoxins, microcystins were named after the first organism discovered to produce them, Microcystis aeruginosa. However it was later found other cyanobacterial genera also produced them.[25] 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.[25]

Blooms containing microcystin are a problem worldwide in freshwater ecosystems.[26] 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.[25] 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.[17] In 2010, a number of sea otters were poisoned by microcystin. Marine bivalves were the likely source of hepatotoxic shellfish poisoning. This was the first confirmed example of a marine mammal dying from ingesting a cyanotoxin.[7]

Nodularins

The first nodularin variant to be identified was nodularin-R, produced by the cyanobacterium Nodularia spumigena.[27] 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.[28] (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.[17]

Alkaloids

Alkaloids are a group of naturally occurring chemical compounds which mostly contain basic nitrogen atoms. They are produced by a large variety of organisms, including cyanobacteria, and are part of the group of natural products, also called secondary metabolites. Alkaloids act on diverse metabolic systems in humans and other animals, often with psychotropic or toxic effects. Almost uniformly, they are bitter tasting.[29]

Anatoxin-a

Investigations into 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.[30] [31] 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.[32]

Toxic effects from anatoxin-a progress very rapidly because it acts directly on the nerve cells (neurons) as a neurotoxin. The progressive symptoms of anatoxin-a exposure are loss of coordination, twitching, convulsions and rapid death by respiratory paralysis. The nerve tissues which communicate with muscles contain a 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.[33] [34]

The toxin was called the Very Fast Death Factor because it induced tremors, paralysis and death within a few minutes when 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.[35] [36] Structurally, it is similar to cocaine.[37] 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.[1] The deadliness of the toxin means that it has a high military potential as a toxin weapon.[4]

Cylindrospermopsins

Cylindrospermopsin (abbreviated to CYN or CYL) was first discovered after an outbreak of a mystery disease on Palm Island in Australia.[38] 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 synthesis was achieved in 2000. Several variants of cylindrospermopsin, both toxic and non-toxic, have been isolated or synthesised.[39]

Cylindrospermopsin is toxic to liver and kidney tissue and is thought to inhibit protein synthesis and to covalently modify DNA and/or RNA. There is concern about the way cylindrospermopsin bioaccumulates in freshwater organisms.[40] 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.[25]

Saxitoxins

Saxitoxin (STX) is one of the most potent natural neurotoxins 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.).[41] Puffer fish and some marine dinoflagellates also produce saxitoxin.[42] [43] Saxitoxins bioaccumulate in shellfish and certain finfish. Ingestion of saxitoxin, usually through shellfish contaminated by toxic algal blooms, can result in paralytic shellfish poisoning.[17]

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.[44] Saxitoxin was originally isolated and described by the United States military, who assigned it the chemical weapon designation "TZ". Saxitoxin is listed in schedule 1 of the Chemical Weapons Convention.[45] According to the book Spycraft, U-2 spyplane pilots were provided with needles containing saxitoxin to be used for suicide in the event escape was impossible.[46]

Lipopolysaccharides

Lipopolysaccharides 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.[47]

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.[48] [49] The exact mechanisms of BMAA toxicity on neuron cells is being investigated. Research suggests both acute and chronic mechanisms of toxicity.[50] [51] BMAA is being investigated as a potential environmental risk factor for neurodegenerative diseases, including ALS, Parkinson's disease and Alzheimer's disease.[52]

Gallery

Other cyanotoxins:

See also
Notes
  1. Stewart I, Seawright AA, Shaw GR (2008). "Cyanobacterial poisoning in livestock, wild mammals and birds – an overview" (PDF). Cyanobacterial Harmful Algal Blooms: State of the Science and Research Needs. Advances in Experimental Medicine and Biology. 619: 613–637. ISBN 978-0-387-75864-0. doi:10.1007/978-0-387-75865-7_28.
  2. Stewart I, Webb PM, Schluter PJ, Shaw GR (2006). "Recreational and occupational field exposure to freshwater cyanobacteria – a review of anecdotal and case reports, epidemiological studies and the challenges for epidemiologic assessment". Environmental Health. 5 (1): 6. doi:10.1186/1476-069X-5-6.
  3. Holtcamp, W. (2012). "The emerging science of BMAA: do cyanobacteria contribute to neurodegenerative disease?". Environmental Health Perspectives. 120 (3): a110–a116. PMC 3295368Freely accessible. PMID 22382274. doi:10.1289/ehp.120-a110.
  4. Dixit A, Dhaked RK, Alam SI, Singh L (2005). "Military potential of biological neurotoxins". Informa Healthcare. 24 (2): 175–207. doi:10.1081/TXR-200057850.
  5. Francis G (1878). "Poisonous Australian Lake". Nature. 18 (444): 11–12. Bibcode:1878Natur..18...11F. doi:10.1038/018011d0.
  6. Anatoxin Neil Edwards, University of Sussex at Brighton. Updated 1 September 1999. Retrieved 19 January 2011.
  7. Miller MA, Kudela RM, Mekebri A, Crane D, Oates SC, et al. (2010). Thompson R, ed. "Evidence for a Novel Marine Harmful Algal Bloom: Cyanotoxin (Microcystin) Transfer from Land to Sea Otters". PLoS ONE. 5 (9): e12576. Bibcode:2010PLoSO...512576M. PMC 2936937Freely accessible. PMID 20844747. doi:10.1371/journal.pone.0012576.
  8. κύανος, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus
  9. Nabors, Murray W. (2004). Introduction to Botany. San Francisco, CA: Pearson Education, Inc. ISBN 0-8053-4416-0.
  10. 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
  11. Allaby, M ed. (1992). "Algae". The Concise Dictionary of Botany. Oxford: Oxford University Press.
  12. 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.
  13. Castenholz RA (1973) "Ecology of blue-green algae in hotsprings". In: The Biology of Blue-green algae. NG Carr and BA Whitton (eds), pp. 379-414. Blackwell Scientific Publications, Oxford.
  14. Vasconcelos VM, Pereira E (2001). "Cyanobacteria diversity and toxicity in a Wastewater Treatment Plant (Portugal)". Water Research. 35 (5): 1354–1357. PMID 11268858. doi:10.1016/S0043-1354(00)00512-1.
  15. Gerald Karp (19 October 2009). Cell and Molecular Biology: Concepts and Experiments. John Wiley and Sons. pp. 14–. ISBN 978-0-470-48337-4. Retrieved 26 January 2011.
  16. Herrero A and Flores E (editor). (2008). The Cyanobacteria: Molecular Biology, Genomics and Evolution. Caister Academic Press. ISBN 978-1-904455-15-8.
  17. Sivonen K and Jones G (1999) "Cyanobacterial Toxins" Archived 2007-01-24 at the Wayback Machine. In Toxic Cyanobacteria in Water. Chorus I and Bartram J (eds): 41-111. WHO, Geneva. ISBN 0419239308.
  18. Lindsey R and Scott M (2010) What are phytoplankton NASA Earth Observatory.
  19. Harmful algal blooms event response NOAA, Center of Excellence for Great Lakes and Human Health. Accessed 6 August 2014.
  20. Stewart I and Falconer IR (2008) "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.
  21. 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. "IOC-UNESCO Taxonomic Reference List of Harmful Micro Algae (HABs)" Accessed 21 January 2011.
  22. Vasconcelos V (2006). "Eutrophication, toxic cyanobacteria and cyanotoxins: when ecosystems cry for help" (PDF). Limnetica. 25 (1–2): 425–432.
  23. Forc, N.S.W.B.G.A.T. (1992). "Final report of the NSW Blue-Green Algae Task Force". Parramatta: NSW Department of Water Resources.
  24. Herath, G. (1995). "The algal bloom problem in Australian waterways: an economic appraisal". Review of Marketing and Agricultural Economics. 63 (1): 77–86.
  25. Chorus & Bartram, 1999
  26. Pelaez M et al, 2010
  27. Sivonen K, Kononen K, Carmichael WW, Dahlem AM, Rinehart KL, Kiviranta J, Niemela SI (1989). "Occurrence of the hepatotoxic cyanobacterium Nodularia spumigena in the Baltic Sea and structure of the toxin". Appl. Environ. Microbiol. 55 (8): 1990–5. PMC 202992Freely accessible. PMID 2506812.
  28. David P. Fewer DP; Köykkä K; Halinen K; Jokela J; Lyra C; Sivonen K (2009). "Culture-independent evidence for the persistent presence and genetic diversity of microcystin-producing Anabaena (Cyanobacteria) in the Gulf of Finland". Environmental Microbiology. 11 (4): 855–866. PMID 19128321. doi:10.1111/j.1462-2920.2008.01806.x.
  29. Rhoades, David F (1979). "Evolution of Plant Chemical Defense against Herbivores". In Rosenthal, Gerald A.; Janzen, Daniel H. Herbivores: Their Interaction with Secondary Plant Metabolites. New York: Academic Press. p. 41. ISBN 0-12-597180-X.
  30. Carmichael WW, Gorham PR (1978). "Anatoxins from clones of Anabaena flos-aquae isolated from lakes of western Canada". Mitt. Infernal. Verein. Limnol. 21: 285–295.
  31. Carmichael WW, Biggs DF, Gorham PR (1975). "Toxicology and pharmacological action of Anabaena flos-aquae toxin". Science. 187 (4176): 542–544. Bibcode:1975Sci...187..542C. PMID 803708. doi:10.1126/science.803708.
  32. Yang, X (2007) Occurrence of the cyanobacterial neurotoxin, anatoxin-a, in New York State waters ProQuest. ISBN 978-0-549-35451-2.
  33. Wood S. A.; Rasmussen J. P.; Holland P. T.; Campbell R.; Crowe A. L. M. (2007). "First Report of the Cyanotoxin Anatoxin-A from Aphanizomenon issatschenkoi (cyanobacteria)". Journal of Phycology. 43 (2): 356–365. doi:10.1111/j.1529-8817.2007.00318.x.
  34. National Center for Environmental Assessment. "Toxicological Reviews of Cyanobacterial Toxins: Anatoxin-a" NCEA-C-1743
  35. Devlin JP, Edwards OE, Gorham PR, Hunter NR, Pike RK, Stavric B (1977). "Anatoxin-a, a toxic alkaloid from Anabaena flos-aquae NRC-44h". Can. J. Chem. 55 (8): 1367–1371. doi:10.1139/v77-189.
  36. Moore RE (1977). "Toxins from blue-green algae". BioScience. 27 (12): 797–802. JSTOR 1297756. doi:10.2307/1297756.
  37. Metcalf JS and Codd GA (2009) "Cyanobacteria, neurotoxins and water resources: Are there implications for human neurodegenerative disease?" Informa Healthcare, 10(s2): 74-78.
  38. Byth S (July 1980). "Palm Island mystery disease". The Medical Journal of Australia. 2 (1): 40, 42. PMID 7432268.
  39. Griffiths DJ, Saker ML (2003). "The Palm Island mystery disease 20 years on: a review of research on the cyanotoxin cylindrospermopsin". Environ Toxicol. 18 (2): 78–93. PMID 12635096. doi:10.1002/tox.10103.
  40. Kinnear S (2010). "Cylindrospermopsin: A Decade of Progress on Bioaccumulation Research". Marine Drugs. 8: 542–564. doi:10.3390/md8030542.
  41. Clark RF, Williams SR, Nordt SP, Manoguerra AS (1999). "A review of selected seafood poisonings". Undersea Hyperb Med. 26 (3): 175–84. PMID 10485519. Retrieved 2008-08-12.
  42. Nakamuraa M, Oshimaa Y, Yasumoto T (1984). "Occurrence of saxitoxin in puffer fish". Toxicon. 22 (3): 381–385. PMID 6474491. doi:10.1016/0041-0101(84)90082-5.
  43. Landsberg JH (2002). "The effects of harmful algal blooms on aquatic organisms". Reviews in Fisheries Science. 10 (2): 113–390. doi:10.1080/20026491051695.
  44. 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.
  45. Chemical Weapons Convention: Schedule 1 Archived 2013-06-07 at the Wayback Machine. Organisation for the Prohibition of Chemical Weapons, The Hague, Netherlands. Retrieved 26 January 2011.
  46. 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.
  47. Stewart I, Schluter PJ, Shaw GR (2006). "Cyanobacterial lipopolysaccharides and human health - a review". Environ Health. 5 (1): 7. PMC 1489932Freely accessible. PMID 16563160. doi:10.1186/1476-069X-5-7.
  48. Cox, PA; Banack, SA; Murch, SJ; Rasmussen, U; Tien, G; Bidigare, RR; Metcalf, JS; Morrison, LF; Codd, GA; Bergman, B. (2005). "Diverse taxa of cyanobacteria produce b-N-methylamino-L-alanine, a neurotoxic amino acid". PNAS. 102 (14): 5074–5078. Bibcode:2005PNAS..102.5074C. PMC 555964Freely accessible. PMID 15809446. doi:10.1073/pnas.0501526102.
  49. Esterhuizen, M; Downing, TG. (2008). "β-N-methylamino-L-alanine (BMAA) in novel South African cyanobacterial isolates". Ecotoxicology and Environmental Safety. 71 (2): 309–313. PMID 18538391. doi:10.1016/j.ecoenv.2008.04.010.
  50. Weiss, JH, Koh, J, Choi. D. (1989). "Neurotoxicity of β -N-methylamino-L-alanine (BMAA) and β-N-oxalylamino-L-alanine (BOAA) on cultured cortical neurons". Brain Research. 497: 64–71. PMID 2551452. doi:10.1016/0006-8993(89)90970-0.
  51. Lobner, D; Piana, PM; Salous, AK; Peoples, RW. (2007). "β-N-methylamino-L-alanine enhances neurotoxicity through multiple mechanisms". Neurobiology of Disease. 25 (2): 360–366. PMC 3959771Freely accessible. PMID 17098435. doi:10.1016/j.nbd.2006.10.002.
  52. Cox, PA, Davis, DA, Mash, DC, Metcalf, JS, Banack, SA. (2015). "Dietary exposure to an environmental toxin triggers neurofibrillary tangles and amyloid deposits in the brain". Proceedings of the Royal Society B. 283 (1823): 20152397. PMC 4795023Freely accessible. PMID 26791617. doi:10.1098/rspb.2015.2397.
References
External links
Continue Reading...
Content from Wikipedia Licensed under CC-BY-SA.

Cyanotoxin

topic

Cyanotoxins are toxins 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 to form blooms . Blooming cyanobacteria can produce cyanotoxins in such concentrations that they 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 . 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 . Despite the similarity in name, they are not cyanides . Recreational exposure to cyanobacteria can result in gastro-intestinal and hay fever symptoms or pruritic skin rashes. Exposure to the cyanobacteria neurotoxin BMAA may be an environmental cause of neurodegenerative diseases s ...more...



Shellfish poisoning

topic

Shellfish poisoning includes four (4) syndromes that share some common features and are primarily associated with bivalve molluscs (such as mussels , clams , oysters and scallops .) These shellfish are filter feeders and, therefore, accumulate toxins produced by microscopic algae , such as cyanobacteria , diatoms and dinoflagellates . Syndromes The syndromes are: Amnesic shellfish poisoning (ASP) Diarrheal shellfish poisoning (DSP) Neurotoxic shellfish poisoning (NSP) Paralytic shellfish poisoning (PSP) See also Cyanotoxin Gonyaulax References Silver, Mary Wilcox (2006), "Protecting Ourselves from Shellfish Poisoning", American Scientist, 94 (4): 316–325, doi : 10.1511/2006.60.316 External links Human Illness Associated with Harmful Algae Shellfish poisoning includes four (4) syndromes that share some common features and are primarily associated with bivalve molluscs (such as mussels , clams , oysters and scallops .) These shellfish are filter feeders and, therefore, accumulate toxins produced by microscopi ...more...



Aphanizomenon

topic

Aphanizomenon is an important genus of cyanobacteria that inhabits freshwater lakes and can cause dense blooms. Studies on the species Aphanizomenon flos-aquae have shown that it can regulate buoyancy through light-induced changes in turgor pressure. It is also able to move by means of gliding, though the specific mechanism by which this is possible is not yet known. Ecology Overcoming phosphate limitation Aphanizomenon may become dominant in a water body partially due to their ability to induce phosphate-limitation in other phytoplankton while also increasing phosphate availability to itself through release of cylindrospermopsin . The cylindrospermopsin causes other phytoplankton to increase their alkaline phosphatase activity, increasing inorganic phosphate availability in the water to Aphanizomenon during times when phosphate becomes limiting. Nitrogen fixation Aphanizomenon is capable of producing biologically-useful nitrogen ( ammonium ) by the process of nitrogen fixation from atmospheric nitrogen by ...more...



Anatoxin-a(S)

topic

Anatoxin-a(S) "Salivary" is a naturally occurring cyanotoxin commonly isolated from cyanobacteria (specifically of the genus Anabaena) and causes excess salivation in mammals via inhibition of acetylcholinesterase . Anatoxin-a(S) is structurally a cyclic N-hydroxyguanine organophosphate with a phosphate ester moiety. Toxicity And Treatment The main mechanism of action for anatoxin-a(S) is by irreversibly inhibiting the active site of acetylcholinesterase leading to excess acetylcholine in the parasympathetic and peripheral nervous systems; inducing poisoning via nicotinic and muscarinic cholinergic receptor stimulation. Treatment of afflicted case by atropine has attested to suppress the muscarinic mediated toxicity; which prevents the namesake salivation that similarly reacts to prevent the toxin's other poisoning symptoms which include lacrimation, urinary incontinence and defecation. Atropine will not, however, counter another mechanism of the compounds toxicity as it also mediates a nicotinic adverse to ...more...



Anatoxin-a

topic

Anatoxin-a , also known as Very Fast Death Factor ( VFDF ), is a secondary, bicyclic amine alkaloid and cyanotoxin with acute neurotoxicity . It was first discovered in the early 1960s in Canada, and was isolated in 1972. The toxin is produced by seven different genera of cyanobacteria and has been reported in North America, South America, Central America, Europe, Africa, Asia, and New Zealand. Symptoms of anatoxin exposure include loss of coordination , muscular fasciculations , convulsions and death by respiratory paralysis . Its mode of action is through the nicotinic acetylcholine receptor (nAchR) where it mimics the binding of the receptor's natural ligand , acetylcholine . As such, anatoxin-a has been used for medicinal purposes to investigate diseases characterized by low acetylcholine levels. Due to its high toxicity and potential presence in drinking water, anatoxin-a poses a threat to animals, including humans. While methods for detection and water treatment exist, scientists have called for more re ...more...



Cylindrospermopsis

topic

Cylindrospermopsis is a planktonic genus of filamentous cyanobacteria known for its blooms in eutrophic waters. The type species is the tropical Cylindrospermopsis raciborskii (Woloszynska) Seenayya & Subbaraju. The cyanotoxin cylindrospermopsin was first identified from a species of this genus. References Patrick J. Walsh; et al., eds. (2008). Oceans and Human Health: Risks and Remedies from the Seas. Amsterdam: Elsevier. pp. 281–282. ISBN   978-0123725844 . Guiry, M.D.; Guiry, G.M. (2008). " Cylindrospermopsis " . AlgaeBase . World-wide electronic publication, National University of Ireland, Galway. Cylindrospermopsis is a planktonic genus of filamentous cyanobacteria known for its blooms in eutrophic waters. The type species is the tropical Cylindrospermopsis raciborskii (Woloszynska) Seenayya & Subbaraju. The cyanotoxin cylindrospermopsin was first identified from a species of this genus. References Patrick J. Walsh; et al., eds. (2008). Oceans and Human Health: Risks and Remedies from the Seas. ...more...



Surface runoff

topic

Surface runoff (also known as overland flow ) is the flow of water that occurs when excess stormwater , meltwater , or other sources flows over the Earth's surface . This might occur because soil is saturated to full capacity, because rain arrives more quickly than soil can absorb it, or because impervious areas ( roofs and pavement ) send their runoff to surrounding soil that cannot absorb all of it. Surface runoff is a major component of the water cycle . It is the primary agent in soil erosion by water . Runoff that occurs on the ground surface before reaching a channel is also called a nonpoint source . If a nonpoint source contains man-made contaminants, or natural forms of pollution (such as rotting leaves) the runoff is called nonpoint source pollution . A land area which produces runoff that drains to a common point is called a drainage basin . When runoff flows along the ground, it can pick up soil contaminants including petroleum , pesticides , or fertilizers that become discharge or nonpoint source ...more...



Nodularia

topic

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 . Some strains produce a cyanotoxin called nodularin R , which is harmful to humans. The type species for the genus is Nodularia spumigena Mertens ex Bornet & Flahault , 1886. Morphology Nodularia may form solitary filaments or groups of filaments. They reproduce by the formation of hormogonia , filament breakage, and by akinetes . See also Kruger, T., Oelmuller, R., and Luckas, B. (2009) Comparative PCR analysis of toxic Nodularia spumigena and non-toxic Nodularia harveyana (Nostocales, Cyanobacteria) with respect to the nodularia synthetase gene cluster. Eur. J. Phycol. 44 (3): 291 - 295. References C. Michael Hogan (2008) Makgadikgadi, The Megalithic Portal, ed. Andy Burnham Jiří Komárek and Tomáš Hauer C ...more...



Microbial toxin

topic

Microbial toxins are toxins produced by micro-organisms, including bacteria and fungi. Microbial toxins promote infection and disease by directly damaging host tissues and by disabling the immune system. Some bacterial toxins, such as Botulinum neurotoxins, are the most potent natural toxins known. However, microbial toxins also have important uses in medical science and research. Potential applications of toxin research include combating microbial virulence, the development of novel anticancer drugs and other medicines, and the use of toxins as tools in neurobiology and cellular biology . Bacterial toxin Bacteria generate toxins which can be classified as either exotoxins or endotoxins . Exotoxins are generated and actively secreted; endotoxins remain part of the bacteria. Usually, an endotoxin is part of the bacterial outer membrane , and it is not released until the bacterium is killed by the immune system . The body's response to an endotoxin can involve severe inflammation . In general, the inflammation ...more...



Palm Island mystery disease

topic

In 1979 an outbreak of hepatoenteritis , also known as the Palm Island mystery disease , was reported and described a hepatitis -like illness (associated in many cases with dehydration and bloody diarrhoea) in 148 people (138 children and 10 adults) of Aboriginal and Torres Strait Islander descent in Palm Island, Queensland . Causes The cause of the outbreak was determined to be the addition of excessive doses of copper sulfate to the water supply of Solomon Dam to target a cyanobacteria bloom of Cylindrospermopsis raciborskii . The excessive dosing was following the use of least-cost contractors to control the algae, who were unqualified in the field. Toxins from the cyanobacteria itself had also been described as a possible cause. Early suggestions included Toxocariasis . Presentation Symptoms of hepatoenteritis included diarrhoea, vomiting attacks, loss of balance and disorientation. The perinatal effects of cyanobacteria contamination of drinking water include prematurity , low birth weight and congenit ...more...



Microcystinase

topic

Microcystinase is a protease that selectively degrades Microcystin , an extremely potent cyanotoxin that results in marine pollution and human and animal food chain poisoning. The enzyme is naturally produced by a number of bacteria isolated in Japan and New Zealand . As of 2012, the chemical structure of this enzyme has not been scientifically determined. The enzyme degrades the cyclic peptide toxin microcystin into a linear peptide, which is 160 times less toxic. Other bacteria then further degrade the linear peptide. Refs "Heterologous expression and characterisation of microcystinase.". Toxicon. 59 (5): 578–86. Apr 2012. PMID   22326726 . doi : 10.1016/j.toxicon.2012.01.001 . http://www.hindawi.com/journals/isrn.microbiology/2013/596429/ Microcystinase is a protease that selectively degrades Microcystin , an extremely potent cyanotoxin that results in marine pollution and human and animal food chain poisoning. The enzyme is naturally produced by a number of bacteria isolated in Japan and New Zealand . A ...more...



Phytoplankton

topic

Phytoplankton are the autotrophic (self-feeding) components of the plankton community and a key part of oceans, seas and freshwater basin ecosystems . The name comes from the Greek words φυτόν (phyton), meaning " plant ", and πλαγκτός (planktos), meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye . However, when present in high enough numbers, some varieties may be noticeable as colored patches on the water surface due to the presence of chlorophyll within their cells and accessory pigments (such as phycobiliproteins or xanthophylls ) in some species. Ecology Phytoplankton come in many shapes and sizes. Phytoplankton are the foundation of the oceanic food chain. When two currents collide (here the Oyashio and Kuroshio currents) they create eddies . Phytoplankton concentrates along the boundaries of the eddies, tracing the motion of the water. Algal bloom off south England. Phytoplankton are photosynthesizing microscopic organisms that inhabit the up ...more...



Toxic encephalopathy

topic

Toxic encephalopathy is a neurologic disorder caused by exposure to neurotoxic organic solvents such as toluene , following exposure to heavy metals such as manganese ; or exposure to extreme concentrations of any natural toxin such as cyanotoxins found in shellfish or freshwater cyanobacteria crusts. Toxic encephalopathy can occur following acute or chronic exposure to neurotoxicants, which includes all natural toxins. Exposure to toxic substances can lead to a variety of symptoms, characterized by an altered mental status, memory loss, and visual problems. Toxic encephalopathy can be caused by various chemicals, some of which are commonly used in everyday life, or cyanotoxins which are bio-accumulated from Harmful algal blooms (HAB's) which have settled on the benthic layer of a waterbody. Toxic encephalopathy can permanently damage the brain and currently treatment is mainly just for the symptoms. Signs and symptoms "Encephalopathy" is a general term describing brain malfunctions and "toxic" asserts that t ...more...



Microcystis aeruginosa

topic

Microcystis aeruginosa is a species of freshwater cyanobacteria which can form harmful algal blooms of economic and ecological importance. They are the most common toxic cyanobacterial bloom in eutrophic fresh water. Cyanobacteria produce neurotoxins and peptide hepatotoxins, such as microcystin and cyanopeptolin . Characteristics NOAA MERIS image of large cyanobacterial bloom confirmed as M. aeruginosa As the etymological derivation implies, Microcystis is characterized by small cells (of only a few micrometers diameter), which lack individual sheaths. Cells usually are organized into colonies (large colonies of which may be viewed with the naked eye) that begin in a spherical shape, but lose their coherence to become perforated or irregularly shaped over time. The protoplast is a light blue-green color, appearing dark or brown due to optical effects of gas-filled vesicles ; this can be useful as a distinguishing characteristic when using light microscopy . These vesicles provide the buoyancy necessary for ...more...



Zooplankton

topic

Zooplankton (pronounced in several different ways, including or . ) are heterotrophic (sometimes detritivorous ) plankton . Plankton are organisms drifting in oceans , seas , and bodies of fresh water . The word "zooplankton" is derived from the Greek zoon ( ζῴον ), meaning "animal", and planktos ( πλαγκτός ), meaning "wanderer" or "drifter". Individual zooplankton are usually microscopic , but some (such as jellyfish) are larger and visible with the naked eye. Ecology A copepod ( Calanoida sp.) A jellyfish ( Aequorea victoria ) Zooplankton is a categorization spanning a range of organism sizes including small protozoans and large metazoans . It includes holoplanktonic organisms whose complete life cycle lies within the plankton, as well as meroplanktonic organisms that spend part of their lives in the plankton before graduating to either the nekton or a sessile , benthic existence. Although zooplankton are primarily transported by ambient water currents, many have locomotion , used to avoid predators (as in ...more...



Cyanopeptolin

topic

Cyanopeptolins are a class of oligopeptides produced by Microcystis and Planktothrix algae strains, and can be neurotoxic . The production of cyanopeptolins occurs through nonribosomal peptides synthases (NRPS). Characteristics Increased water temperatures, because of climate change and eutrophication of inland waters promote blooms of cyanobacteria , potentially threaten water contamination by the production of the toxic cyanopeptolin (CP1020). Exposure Cyanopeptolin (CP1020) exposure in zebrafish affected pathways related to DNA damage, the circadian rhythm and response to light. See also Cyanotoxin Microviridin Microcystin References Susanne Faltermann, Sara Zucchi, Esther Kohler, Judith F. Blom, Jakob Pernthaler, Karl Fent (April 2014). "Molecular effects of the cyanobacterial toxin cyanopeptolin (CP1020) occurring in algal blooms: Global transcriptome analysis in zebrafish embryos" . Aquatic Toxicology. 149 : 33–39. doi : 10.1016/j.aquatox.2014.01.018 . Karl Gademann, Cyril Portmann, Judith F. Blom, M ...more...



Aplysiatoxin

topic

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 . While this action has a tumour-promoting effect, protein kinase C activation can be medically beneficial for some other applications, and synthetic analogues of aplysiatoxin have been researched for anti-cancer effects. See also Debromoaplysiatoxin References Kato Y, Scheuer PJ. Aplysiatoxin and debromoaplysiatoxin, constituents of the marine mollusk Stylocheilus longicauda (Quoy and Gaimard, 1824). Journal of the American Chemical Society. 1974 Apr 3;96(7):2245-6. PMID   4833645 Weinstein IB, Arcoleo J, Backer J, Jeffrey A, Hsiao WL, Gattoni-Celli S, Kirschmeier P, Okin E. Molecular mechanisms of tumor promotion and multistage carcinogenesis. Princess Takamatsu Symposia. 1983;14:59-74. PMID   6097583 Arcoleo JP, Weinstein IB. Activation of protein k ...more...



Marine debris

topic

Marine debris on the Hawaiian coast Marine debris , also known as marine litter , is human-created waste that has deliberately or accidentally been released in a lake , sea , ocean or waterway . Floating oceanic debris tends to accumulate at the center of gyres and on coastlines , frequently washing aground, when it is known as beach litter or tidewrack. Deliberate disposal of wastes at sea is called ocean dumping. Naturally occurring debris, such as driftwood , are also present. With the increasing use of plastic , human influence has become an issue as many types of plastics do not biodegrade . Waterborne plastic poses a serious threat to fish , seabirds , marine reptiles , and marine mammals , as well as to boats and coasts. Dumping, container spillages, litter washed into storm drains and waterways and wind-blown landfill waste all contribute to this problem. Types of debris Debris on beach near Dar es Salaam , Tanzania Debris collected from beaches on Tern Island in the French Frigate Shoals over one m ...more...



Lyngbyatoxin-a

topic

Lyngbyatoxin-a is a cyanotoxin produced by certain cyanobacteria species, most notably Moorea producens (formerly Lyngbya majuscula). It is produced as defense mechanism to ward off any would-be predators of the bacterium, being a potent blister agent as well as carcinogen . Low concentrations cause a common skin condition known as seaweed dermatitis . Biosynthesis Lyngbyatoxin Biosynthesis reported by Gerwick et al. and Neilan et al. Lyngbyatoxin is a terpenoid indole alkaloid that belongs to the class of non-ribosomal peptides (NRP). Lyngbyatoxin contains a nucleophilic indole ring that takes part in the activation of protein kinases. Figure 1, shows the biosynthesis of Lyngbyatoxin reported by Neilan et al. and Gerwick et al.The non-ribosomal peptide synthase (NRPS) LtxA protein condenses L-methyl-valine and L-tryptophan to form the linear dipeptide N-methyl-L-valyl-L-tryptophan. The latter is released via a NADPH-dependent reductive cleavage to form the aldehyde which is subsequently reduced to the corre ...more...



Marine pollution

topic

Marine pollution occurs when harmful, or potentially harmful, effects result from the entry into the ocean of chemicals, particles , industrial , agricultural, and residential waste , noise, or the spread of invasive organisms . Eighty percent of marine pollution comes from land. Air pollution is also a contributing factor by carrying off pesticides or dirt into the ocean. Land and air pollution have proven to be harmful to marine life and its habitats. The pollution often comes from nonpoint sources such as agricultural runoff , wind-blown debris, and dust. Nutrient pollution , a form of water pollution , refers to contamination by excessive inputs of nutrients. It is a primary cause of eutrophication of surface waters, in which excess nutrients, usually nitrates or phosphates , stimulate algae growth. Many potentially toxic chemicals adhere to tiny particles which are then taken up by plankton and benthic animals , most of which are either deposit feeders or filter feeders . In this way, the toxins are conc ...more...



Plankton

topic

Photomontage of planktonic organisms Plankton (singular plankter ) are the diverse collection of organisms that live in large bodies of water and are unable to swim against a current. They provide a crucial source of food to many large aquatic organisms, such as fish and whales . These organisms include bacteria , archaea , algae , protozoa and drifting or floating animals that inhabit—for example—the pelagic zone of oceans , seas , or bodies of fresh water . Essentially, plankton are defined by their ecological niche rather than any phylogenetic or taxonomic classification. Though many planktonic species are microscopic in size, plankton includes organisms over a wide range of sizes, including large organisms such as jellyfish . Technically the term does not include organisms on the surface of the water, which are called pleuston —or those that swim actively in the water, which are called nekton . Terminology Some marine diatoms —a key phytoplankton group The name plankton is derived from the Greek adjecti ...more...



Microviridin

topic

The microviridins are a class of serine protease inhibitors produced by various genera of cyanobacteria . Recent genome mining has shown that the biosynthetic gene cluster responsible for microviridn biosynthesis is much more prevalent, found in many species of Proteobacteria and Bacteriodetes. Microviridins are members of the RiPP family of natural products. The first microviridin was isolated from Microcystis viridis (NIES-102) and its structure was reported in 1990. Microviridins are characterized by a tricyclic depsipeptide structure resulting from the enzymatic activity of two dedicated ATP-grasp ligases, which form two lactone and one lactam rings in the core region of the precursor peptide. Toxicity Microviridin J has been found to disrupt molting in the invertebrate Daphnia pulicaria , probably as a result of its protease inhibitory effects See also Cyanotoxin Cyanopeptolin References Ahmed MN, Reyna-González E, Schmid B, Wiebach V, Süssmuth RD, Dittmann E, Fewer DP (2017). "Phylogenomic Analysis of ...more...



Paralytic shellfish poisoning

topic

Paralytic shellfish poisoning ( PSP ) is one of the four recognized syndromes of shellfish poisoning , which share some common features and are primarily associated with bivalve mollusks (such as mussels , clams , oysters and scallops ). These shellfish are filter feeders and accumulate neurotoxins , chiefly saxitoxin , produced by microscopic algae , such as dinoflagellates , diatoms , and cyanobacteria . Dinoflagellates of the genus Alexandrium are the most numerous and widespread saxitoxin producers and are responsible for PSP blooms in subarctic, temperate, and tropical locations. The majority of toxic blooms have been caused by the morphospecies Alexandrium catenella , Alexandrium tamarense , and Alexandrium fundyense , which together comprise the A. tamarense species complex. In Asia, PSP is mostly associated with the occurrence of the species Pyrodinium bahamense. Also some pufferfish, including chamaeleon puffer , contain saxitoxin, making their consumption hazardous. Pathophysiology The toxins res ...more...



Anabaena circinalis

topic

Anabaena circinalis is a species of Gram-negative, photosynthetic cyanobacteria common to freshwater environments throughout the world. Much of the scientific interest in A. circinalis owes to its production of several potentially harmful cyanotoxins, ranging in potency from irritating to lethal. Under favorable conditions for growth, A. circinalis forms large algae-like blooms, potentially harming the flora and fauna of an area. Morphology Anabaena circinalis from Hungary Anabaena circinalis exhibits a filamentous morphology, each filament a string of task-specific cells. The appearance of cell differentiation was a great evolutionary leap; marking cyanobacteria as one of the first multicellular organisms on Earth. On the A. circinalis filament, the most numerous structures are vegetative cells , responsible for the photosynthesis of high-energy sugars from environmental carbon, water, and sunlight. The energy from photosynthesis is used, in part, for the biosynthesis of cellular materials from nitrogenous ...more...



Microcystin-LR

topic

Microcystin-LR ( MC-LR ) is a toxin produced by cyanobacteria . It is the most toxic of the microcystins . History The Chinese general Zhu-Ge Liang was the first to observe cyanobacteria poisoning about 1000 years ago. He reported the death of troops who drank green coloured water from a river in southern China. The first published report of an incidence of cyanobacteria poisoning dates from the poisoning of an Australian lake in 1878. Also, in China and Brasil, people died after drinking water from a lake. All these incidents have been attributed to cyanobacteria and the toxic compound microcystin-LR. That is the reason why the World Health Organisation (WHO) issued a guideline for microcystins in drinking water. The WHO guideline for microcystins in drinking water, based on microcystin-LR, is 1 μg/L. With the high levels of Eutrophication in South Africa, typical exposures can be as high as 10 μg/L. Structure Microcystins are cyclic heptapeptides . The seven amino acids that are involved in the structure ...more...



Drought

topic

Contraction/Desiccation cracks in dry earth ( Sonoran desert , Mexico ). A drought is a period of below-average precipitation in a given region, resulting in prolonged shortages in the water supply, whether atmospheric, surface water or ground water . A drought can last for months or years, or may be declared after as few as 15 days. It can have a substantial impact on the ecosystem and agriculture of the affected region and harm to the local economy . Annual dry seasons in the tropics significantly increase the chances of a drought developing and subsequent bush fires. Periods of heat can significantly worsen drought conditions by hastening evaporation of water vapour . Many plant species, such as those in the family Cactaceae (or cacti ), have drought tolerance adaptations like reduced leaf area and waxy cuticles to enhance their ability to tolerate drought. Some others survive dry periods as buried seeds. Semi-permanent drought produces arid biomes such as deserts and grasslands. Prolonged droughts hav ...more...



Cyanobacteria

topic

Cyanobacteria , also known as Cyanophyta , is a phylum of bacteria that obtain their energy through photosynthesis , and are the only photosynthetic prokaryotes able to produce oxygen. The name "cyanobacteria" comes from the color of the bacteria ( Greek : κυανός (kyanós) = blue). Cyanobacteria (which are prokaryotes) used to be called "blue-green algae". They have been renamed 'cyanobacteria' in order to avoid the term " algae ", which in modern usage is restricted to eukaryotes . Unlike heterotrophic prokaryotes, cyanobacteria have internal membranes. They are flattened sacs called thylakoids where photosynthesis is performed. Phototrophic eukaryotes perform photosynthesis by plastids that have their ancestry in cyanobacteria, via a process called endosymbiosis . These endosymbiotic cyanobacteria in eukaryotes have evolved or differentiated into specialized organelles such as chloroplasts , etioplasts and leucoplasts . By producing and releasing oxygen (as a byproduct of photosynthesis), cyanobacteria are ...more...



Microcystin

topic

Microcystins — or cyanoginosins — are a class of toxins produced by certain freshwater cyanobacteria ; primarily Microcystis aeruginosa but also other Microcystis , as well as members of the Planktothrix , Anabaena , Oscillatoria and Nostoc genera. Over 50 different microcystins have been discovered so far, of which microcystin-LR is the most common. Chemically they are cyclic heptapeptides produced through nonribosomal peptide synthases. Microcystins can be produced in large quantities during algal blooms and pose a major threat to drinking and irrigation water supplies, as well as the environment at large. Characteristics Chemical structure of microcystin-LR Microcystin-LR is the most toxic form of over 80 known toxic variants, and is also the most studied by chemists, pharmacologists, biologists, and ecologists. Microcystin-containing 'blooms' are a problem worldwide, including China, Brazil, Australia, South Africa, the United States and much of Europe. Hartebeespoort Dam in South Africa is one ...more...



Single-cell protein

topic

Single-cell protein ( SCP ) refers to edible unicellular microorganisms . The biomass or protein extract from pure or mixed cultures of algae , yeasts , fungi or bacteria may be used as an ingredient or a substitute for protein-rich foods, and is suitable for human consumption or as animal feeds. Whereas industrial agriculture is marked by a high water footprint , high land use, biodiversity destruction, general environmental degradation and contributes to climate change by emission of a third of all greenhouse gases , production of SCP does not necessarily exhibit any of these serious drawbacks. As of today, SCP is commonly grown on agricultural waste products, and as such inherits the ecological footprint and water footprint of industrial agriculture. However, SCP may also be produced entirely independent of agricultural waste products through autotrophic growth. Thanks to the high diversity of microbial metabolism, autotrophic SCP provides several different modes of growth, versatile options of nutri ...more...



Aphanizomenon flos-aquae

topic

Aphanizomenon flos-aquae is a brackish and freshwater species of cyanobacteria found around the world, including the Baltic Sea and the Great Lakes . Ecology Aphanizomenon flos-aquae bloom on the Upper Klamath Lake , Oregon Aphanizomenon flos-aquae can form dense surface aggregations in freshwater (known as "cyanobacterial blooms"). These blooms occur in areas of high nutrient loading , historical or current. Toxicity Aphanizomenon flos-aquae has both toxic and nontoxic forms. Most sources worldwide are toxic, containing both hepatic and neuro endotoxins . Most cyanobacteria (including Aphanizomenon) produce BMAA , a neurotoxin amino acid implicated in ALS / Parkinsonism . Toxicity of A. flos-aquae has been reported in Canada, Germany and China. Aphanizomenon flos-aquae is known to produce endotoxins , the toxic chemicals released when cells die. Once released ( lysed ), and ingested, these toxins can damage liver and nerve tissues in mammals. In areas where water quality is not closely monitored, the W ...more...



Nonribosomal peptide

topic

Nonribosomal peptides ( NRP ) are a class of peptide secondary metabolites , usually produced by microorganisms like bacteria and fungi . Nonribosomal peptides are also found in higher organisms, such as nudibranchs , but are thought to be made by bacteria inside these organisms. While there exist a wide range of peptides that are not synthesized by ribosomes , the term nonribosomal peptide typically refers to a very specific set of these as discussed in this article. Nonribosomal peptides are synthesized by nonribosomal peptide synthetases , which, unlike the ribosomes , are independent of messenger RNA . Each nonribosomal peptide synthetase can synthesize only one type of peptide. Nonribosomal peptides often have cyclic and/or branched structures, can contain non- proteinogenic amino acids including D -amino acids, carry modifications like N -methyl and N-formyl groups, or are glycosylated , acylated , halogenated , or hydroxylated . Cyclization of amino acids against the peptide "backbone" is often perfor ...more...



Apratoxin A

topic

Apratoxin A - is a cyanobacterial secondary metabolite, known as a potent cytotoxic marine natural product . It is a derivative of the Apratoxin family of cytotoxins. The mixed peptide-polyketide natural product comes from a polyketide synthase/non-ribosomal peptide synthase pathway (PKS/NRPS). This cytotoxin is known for inducing G1-phase cell cycle arrest and apoptosis . This natural product's activity has made it a popular target for developing anticancer derivatives. Structural Characteristics and Determination Apratoxin A is a mixed peptide-polyketide cyclic structure, as shown above. It has a thiazoline ring flanked by polyketide segments, one of which has an unusual methylation pattern. The structure has been elucidated by spectral analysis, including several 2D NMR techniques. The absolute configuration of the amino acid segments was determined by chiral HPLC analysis. Biosynthesis Apratoxin A is comes from the Apratoxin biosynthetic pathway. Figure 1 describes a proposed Biosynthetic pathway ...more...



Cyclamide

topic

Cyclamides are a class of oligopeptides , produced by cyanobacteria algae strains, such as microcystis aeruginosa and can be toxic. Cyclamides are synthesized through ribosomic pathways. See also Cyanopeptolin Microcystin References Ramsy Agha; Samuel Cirés; Lars Wörmer & Antonio Quesada (2013). "Limited Stability of Microcystins in Oligopeptide Compositions of Microcystis aeruginosa (Cyanobacteria): Implications in the Definition of Chemotypes" . Toxins. 5 : 1089–1104. PMC   3717771   . PMID   23744054 . doi : 10.3390/toxins5061089 . Cyril Portmann; Judith F. Blom; Karl Gademann & Friedrich Jüttner (2008). "Aerucyclamides A and B: Isolation and Synthesis of Toxic Ribosomal Heterocyclic Peptides from the Cyanobacterium Microcystis aeruginosa PCC 7806" . J. Nat. Prod. 71 : 1193–6. PMID   18558743 . doi : 10.1021/np800118g . External links Cyanobacteria, and toxin production (The New York Times) Cyclamides are a class of oligopeptides , produced by cyanobacteria algae strains, such as microcystis aeru ...more...



Cylindrospermopsin

topic

Cylindrospermopsin (abbreviated to CYN , or CYL ) 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 synthesis and to covalently modify DNA and/or RNA . It is not known whether cylindrospermopsin is a carcinogen , but it appears to have no tumour initiating activity in mice. CYN was first discovered after an outbreak of a mystery disease on Palm Island , Queensland , 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 in 1992, which was revised after synthesis was achieved in 2000. Several analogues of CYN, both toxic and non-toxic, have been isolated or synthesised. C. raciborskii has been observed mainly in tropi ...more...



Sea otter

topic

The sea otter (Enhydra lutris) is a marine mammal native to the coasts of the northern and eastern North Pacific Ocean . Adult sea otters typically weigh between 14 and 45 kg (31 and 99 lb), making them the heaviest members of the weasel family , but among the smallest marine mammals. Unlike most marine mammals, the sea otter's primary form of insulation is an exceptionally thick coat of fur , the densest in the animal kingdom. Although it can walk on land, the sea otter lives mostly in the ocean. The sea otter inhabits offshore environments, where it dives to the sea floor to forage . It preys mostly on marine invertebrates such as sea urchins , various molluscs and crustaceans , and some species of fish . Its foraging and eating habits are noteworthy in several respects. First, its use of rocks to dislodge prey and to open shells makes it one of the few mammal species to use tools. In most of its range, it is a keystone species , controlling sea urchin populations which would otherwise inflict extensive dam ...more...



Debromoaplysiatoxin

topic

Debromoaplysiatoxin is a toxic agent produced by the blue-green alga Lyngbya majuscula . This alga lives in marine waters and causes seaweed dermatitis . Furthermore, it is a tumor promoter which has an anti-proliferative activity against various cancer cell lines in mice. History The first reported case of seaweed dermatitis was from 1958 in Hawaii on Oahu island. About 125 people who had been swimming in the sea get suffered from symptoms like itching, burning, blisters, rash and desquamation. The causative substance of this seaweed dermatitis was not known till 1968 when people in Okinawa, Japan, suffered from the same symptoms as the people in Hawaii. After researchers took samples in 1973 from Lyngbya majuscula they found out that this was the causative agent of the dermatitis. In 1980 there was a new outbreak of seaweed dermatitis on Oahu island Hawaii. Samples of L. majuscula revealed that this blue-green alga contained a mixture of aplysiatoxin , debromoaplysiatoxin and lyngbyatoxin A . These three su ...more...



Coibamide

topic

Coibamide A is an antiproliferative depsipeptide which was isolated from a marine Leptolyngbya cyanobacterium . Testing of coibamide A in the National Cancer Institute in vitro 60 human tumor cell line panel (NCI-60) revealed potent anti-proliferative activity and a unique selectivity profile. Similarities between coibamide A- and apratoxin A -induced changes in cell morphology, decreases in VEGFR2 expression and macroautophagy signaling in HUVECs raise the possibility that both cyanobacterial natural products share a common mechanism of action. Wild-type mouse embryonic fibroblasts were more vulnerable to coibamide A than cells lacking autophagy-related protein 5 ( Atg5 ) that suggest coibamide A as a compound with characteristics that may utilize autophagy for pro-death signaling. Solid-phase total syntheses of highly methylated cyclic azacoibamide A and its O-desmethyl analog were achieved to improve pharmacokinetic properties of coibamide A. References Medina, Rebecca A.; Goeger, Douglas E.; Hills, Patr ...more...



Algae fuel

topic

Algae fuel , algal biofuel , or algal oil is an alternative to liquid fossil fuels that uses algae as its source of energy-rich oils. Also, algae fuels are an alternative to commonly known biofuel sources, such as corn and sugarcane. Several companies and government agencies are funding efforts to reduce capital and operating costs and make algae fuel production commercially viable. Like fossil fuel, algae fuel releases CO when burnt, but unlike fossil fuel, algae fuel and other biofuels only release CO recently removed from the atmosphere via photosynthesis as the algae or plant grew. The energy crisis and the world food crisis have ignited interest in algaculture (farming algae) for making biodiesel and other biofuels using land unsuitable for agriculture. Among algal fuels' attractive characteristics are that they can be grown with minimal impact on fresh water resources, can be produced using saline and wastewater , have a high flash point , and are biodegradable and relatively harmless to the envir ...more...

Member feedback about Algae fuel:

Folder: Tahir Farooque

(TahirFarooqueArain)

chlorella for waste watere


Marine bacteriophage

topic

Marine bacteriophages or marine phages are viruses that live as obligate parasitic agents in marine bacteria such as cyanobacteria . Their existence was discovered through electron microscopy and epifluorescence microscopy of ecological water samples, and later through metagenomic sampling of uncultured viral samples. The tailed bacteriophages appear to dominate marine ecosystems in number and diversity of organisms. However, viruses belonging to families Corticoviridae , Inoviridae and Microviridae are also known to infect diverse marine bacteria. Metagenomic evidence suggests that microviruses (icosahedral ssDNA phages) are particularly prevalent in marine habitats. Bacteriophages , viruses that are parasitic on bacteria, were first discovered in the early twentieth century. Scientists today consider that their importance in ecosystems , particularly marine ecosystems , has been underestimated, leading to these infectious agents being poorly investigated and their numbers and species biodiversity being ...more...



Kalkitoxin

topic

Kalkitoxin , a lipopeptide derived from the cyanobacterium Lyngbya majuscula , induces NMDA receptor mediated neuronal necrosis, blocks voltage-dependent sodium channels , and induces cellular hypoxia by inhibiting the electron transport chain (ETC) complex 1. Natural Sources Kalkitoxin is an ichthyotoxin , derived from the cyanobacterium Lyngbya majuscula which covers sections of the coral reef. It typically forms mini-blooms and produces several metabolites, such as kalkitoxin, curacin-A and antillatoxin . Kalkitoxin has been found and purified near the coasts of Curaçao and Puerto Rico. Structure and Reactivity Kalkitoxin is a lipopeptide toxin with a molecular weight of 366.604Da. Its chemical formula is CHNOS. The structure contains two double bonds, a 2,4-disubstituted thiazoline ring system, and an additional carbonyl-group. These four groups each provide a degree of unsaturation, which causes kalkitoxin to have four degrees of unsaturation . The structure contains 5 chiral centers , one of w ...more...



Excitotoxicity

topic

Low Ca buffering and excitotoxicity under physiological stress and pathophysiological conditions in motor neuron (MNs). Low Ca buffering in amyotrophic lateral sclerosis (ALS) vulnerable hypoglossal MNs exposes mitochondria to higher Ca loads compared to highly buffered cells. Under normal physiological conditions, the neurotransmitter opens glutamate, NMDA and AMPA receptor channels, and voltage dependent Ca channels (VDCC) with high glutamate release, which is taken up again by EAAT1 and EAAT2. This results in a small rise in intracellular calcium that can be buffered in the cell. In ALS, a disorder in the glutamate receptor channels leads to high calcium conductivity, resulting in high Ca loads and increased risk for mitochondrial damage. This triggers the mitochondrial production of reactive oxygen species (ROS), which then inhibit glial EAAT2 function. This leads to further increases in the glutamate concentration at the synapse and further rises in postsynaptic calcium levels, contributing to the s ...more...



Beta-Methylamino-L-alanine

topic

β-Methylamino- L -alanine , or BMAA , is a non-proteinogenic amino acid produced by cyanobacteria . BMAA is a neurotoxin and its potential role in various neurodegenerative disorders is the subject of scientific research. Structure and properties BMAA is a derivative of the amino acid alanine with a methylamino group on the side chain . This non-proteinogenic amino acid is classified as a polar base . Sources and detection BMAA is produced by cyanobacteria in marine, freshwater and terrestrial environments. In cultured non-nitrogen-fixing cyanobacteria, BMAA production increases in nitrogen depleted medium. BMAA has been found in aquatic organisms and in plants with cyanobacterial symbionts such as certain lichens , the floating fern Azolla, the leaf petioles of the tropical flowering plant Gunnera, cycads as well as in animals that eat the fleshy covering of cycad seeds, including flying foxes . High concentrations of BMAA are present in shark fins. Because BMAA is a neurotoxin, consumption of shark fin ...more...



Saxitoxin

topic

Saxitoxin ( STX ) is a potent neurotoxin and the best-known paralytic shellfish toxin (PST). Ingestion of saxitoxin, usually by consumption of shellfish contaminated by toxic algal blooms , is responsible for the human illness known as paralytic shellfish poisoning (PSP). The term saxitoxin originates from the genus name of the butter clam ( Saxidomus ) from which it was first isolated. But the term saxitoxin can also refer to the entire suite of more than 50 structurally related neurotoxins (known collectively as "saxitoxins") produced by algae and cyanobacteria which includes saxitoxin itself (STX), neosaxitoxin (NSTX), gonyautoxins (GTX) and decarbamoylsaxitoxin (dcSTX). Saxitoxin has a large environmental and economic impact, as its presence in bivalve shellfish such as mussels , clams , oysters and scallops frequently leads to bans on commercial and recreational shellfish harvesting in many temperate coastal waters around the world including northeastern and western United States, western Europe, east As ...more...



Vacha Reservoir

topic

Vacha Reservoir ( Bulgarian : Въча язовир Yazovir Vacha; before 1999: Antonivanovtsi Reservoir ) is a body of water associated with a dam in Devin Municipality , south Bulgaria . It is part of the Vacha Cascade Joint Implementation Project involving three more dams and four power stations. The two other existing dams on the Vacha River are the Kamak Dam and the Tsankov Dam ; the Krichim Dam is in the implementation stage. Completed on 5 November 1975, the Vacha Dam is situated 680 metres (2,230 ft) above sea level . The dam was designed by Bulgarian hydroengineers, though their work was overseen by Russian , Japanese and Italian experts. It is a concrete gravity structure of 144.5 metres (474 ft) height, making it the tallest dam in Bulgaria. Its pumped storage power plant has a capacity of 160 MW. History The potential of hydroelectric projects on the Vacha River in southern Bulgaria was recognized by the Bulgarian government at least as early as the early 1960s. The June 1962 edition of Water Power sta ...more...



Safe Drinking Water Act

topic

The Safe Drinking Water Act ( SDWA ) is the principal federal law in the United States intended to ensure safe drinking water for the public. Pursuant to the act, the Environmental Protection Agency (EPA) is required to set standards for drinking water quality and oversee all states , localities, and water suppliers that implement the standards. The SDWA applies to every public water system (PWS) in the United States. There are currently about 155,000 public water systems providing water to almost all Americans at some time in their lives. The Act does not cover private wells. The SDWA does not apply to bottled water . Bottled water is regulated by the Food and Drug Administration (FDA), under the Federal Food, Drug, and Cosmetic Act . National Primary Drinking Water Regulations The SDWA requires EPA to establish National Primary Drinking Water Regulations (NPDWRs) for contaminants that may cause adverse public health effects. The regulations include both mandatory levels ( Maximum Contaminant Levels , or ...more...



Antillatoxin

topic

Antillatoxin ( ATX ) is a potent lipopeptide neurotoxin produced by the marine cyanobacterium Lyngbya majuscula . ATX activates voltage-gated sodium channels , which can cause cell depolarisation, NMDA-receptor overactivity, excess calcium influx and neuronal necrosis. Sources Antillatoxin is found in the venom of the marine cyanobacterium Lyngbya majuscula . The filamentous cyanobacterium grows on seagrass, macroalgae, and corals up to 30m deep in tropical and subtropical regions throughout the world. Structure The three dimensional NMR study of this toxin showed that it consists of a tripeptide glycine-N-methylvaline-alanine, a hydroxycarboxylic acid and a 9-t-butyl-6,8-dimethyl-6,8-diene attached to the C5 atom of the cyclic peptide backbone. Analogs There are three known analogous structures of ATX which have different toxicity: antillatoxin B (8-demethyl-antillatoxin) and DH-ATX (8-demethyl-8,9-dihydro-antillatoxin), and various stereoisomers of antillatoxin A. These various structures have been found ...more...



Luxhay Reservoir

topic

Luxhay Reservoir is an artificial reservoir near Angersleigh , Somerset , England. It is now owned by Wessex Water . It was built in 1905 by the town corporation to provide drinking water for Taunton . The reservoir is fed by other local water sources including Otterhead Lakes and Blagdon reservoir. From 1969 leakage was detected in the retaining dam . This got worse in 1990s remedial works, including a diaphragm wall were undertaken. In 2006 the lake was found to have an intense bloom of Microcystins which was associated high concentrations of cyanotoxins probably associated with eutrophication of nutrient enriched sediments. References Castro, Ana (Spring 2008). "Investigating blooms of microcystis in Luxhay Reservoir in the UK: Preliminary findings" (PDF) . The Phycologist. British Phycological Society. 74 : 16 . Retrieved 6 March 2011 . Millmore, J.P.; Stables, J.F.; Shannon, F.E. (September 1998). "The rehabilitation of Luxha Dam Somerset" (PDF) . Proceedings of Conference. Bangor: British Dam Society. p ...more...



Algal bloom

topic

An algal bloom is a rapid increase or accumulation in the population of algae in freshwater or marine water systems, and is recognized by the discoloration in the water from their pigments. Cyanobacteria were mistaken for algae in the past, so cyanobacterial blooms are sometimes also called algal blooms. Blooms which can injure animals or the ecology are called " harmful algal blooms " (HAB), and can lead to fish die-offs, cities cutting off water to residents, or states having to close fisheries. Blooming Algal blooms can present problems for ecosystems and human society. Since 'algae' is a broad term including organisms of widely varying sizes, growth rates and nutrient requirements, there is no officially recognized threshold level as to what is defined as a bloom. For some species, algae can be considered to be blooming at concentrations reaching millions of cells per milliliter, while others form blooms of tens of thousands of cells per liter. The photosynthetic pigments in the algal cells determine the ...more...



Toxin

topic

A toxin (from Ancient Greek : τοξικόν   toxikon ) is a poisonous substance produced within living cells or organisms; synthetic toxicants created by artificial processes are thus excluded. The term was first used by organic chemist Ludwig Brieger (1849–1919). Toxins can be small molecules , peptides , or proteins that are capable of causing disease on contact with or absorption by body tissues interacting with biological macromolecules such as enzymes or cellular receptors . Toxins vary greatly in their toxicity , ranging from usually minor (such as a bee sting ) to almost immediately deadly (such as botulinum toxin ). Terminology Toxins are often distinguished from other chemical agents by their method of production—the word toxin does not specify method of delivery (compare with venom and the broader meaning of poison —all substances that can also cause disturbances to organisms). It simply means it is a biologically produced poison. There was an ongoing terminological dispute between NATO and the Warsaw ...more...



Non-proteinogenic amino acids

topic

In biochemistry , non-coded or non-proteinogenic amino acids are those not naturally encoded or found in the genetic code of any organism. Despite the use of only 22 amino acids (21 in eukaryotes ) by the translational machinery to assemble proteins (the proteinogenic amino acids ), over 140 amino acids are known to occur naturally in proteins and thousands more may occur in nature or be synthesized in the laboratory. Many non-proteinogenic amino acids are noteworthy because they are; intermediates in biosynthesis, post-translationally formed in proteins, possess a physiological role (e.g. components of bacterial cell walls , neurotransmitters and toxins ), natural or man-made pharmacological compounds, present in meteorites and in prebiotic experiments (e.g. Miller–Urey experiment ). Definition by negation Lysine Technically, any organic compound with an amine (-NH) and a carboxylic acid (-COOH) functional group is an amino acid. The proteinogenic amino acids are small subset of this group that possess cent ...more...




Next Page
Javascript Version
Revolvy Server https://www.revolvy.com