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Cyanobacteria, also called Cyanobacteriota or Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name cyanobacteria refers to their color, which similarly forms the basis of cyanobacteria's common name, blue-green algae, although they are not usually scientifically classified as algae. They appear to have originated in a freshwater or terrestrial environment. Sericytochromatia, the proposed name of the paraphyletic and most basal group, is the ancestor of both the non-photosynthetic group Melainabacteria and the photosynthetic cyanobacteria, also called Oxyphotobacteria.
An oligopeptide, often just called peptide, consists of two to twenty amino acids and can include dipeptides, tripeptides, tetrapeptides, and pentapeptides. Some of the major classes of naturally occurring oligopeptides include aeruginosins, cyanopeptolins, microcystins, microviridins, microginins, anabaenopeptins, and cyclamides. Microcystins are best studied, because of their potential toxicity impact in drinking water. A review of some oligopeptides found that the largest class are the cyanopeptolins (40.1%), followed by microcystins (13.4%).
Microcystins—or cyanoginosins—are a class of toxins produced by certain freshwater cyanobacteria, commonly known as blue-green algae. Over 250 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.
Cyanotoxins are toxins produced by cyanobacteria. Cyanobacteria are found almost everywhere, but particularly in lakes and in the ocean where, under high concentration of phosphorus conditions, they reproduce exponentially to form 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.
Aphanizomenon flos-aquae is a brackish and freshwater species of cyanobacteria found around the world, including the Baltic Sea and the Great Lakes.
Cyanophages are viruses that infect cyanobacteria, also known as Cyanophyta or blue-green algae. Cyanobacteria are a phylum of bacteria that obtain their energy through the process of photosynthesis. Although cyanobacteria metabolize photoautotrophically like eukaryotic plants, they have prokaryotic cell structure. Cyanophages can be found in both freshwater and marine environments. Marine and freshwater cyanophages have icosahedral heads, which contain double-stranded DNA, attached to a tail by connector proteins. The size of the head and tail vary among species of cyanophages. Cyanophages infect a wide range of cyanobacteria and are key regulators of the cyanobacterial populations in aquatic environments, and may aid in the prevention of cyanobacterial blooms in freshwater and marine ecosystems. These blooms can pose a danger to humans and other animals, particularly in eutrophic freshwater lakes. Infection by these viruses is highly prevalent in cells belonging to Synechococcus spp. in marine environments, where up to 5% of cells belonging to marine cyanobacterial cells have been reported to contain mature phage particles.
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.
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 multiple genera of cyanobacteria and has been reported in North America, South America, Central America, Europe, Africa, Asia, and Oceania. Symptoms of anatoxin-a toxicity 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 research to improve reliability and efficacy. Anatoxin-a is not to be confused with guanitoxin, another potent cyanotoxin that has a similar mechanism of action to that of anatoxin-a and is produced by many of the same cyanobacteria genera, but is structurally unrelated.
Cylindrospermopsin is a cyanotoxin produced by a variety of freshwater cyanobacteria. CYN is a polycyclic uracil derivative containing guanidino and sulfate groups. It is also zwitterionic, making it highly water soluble. CYN is toxic to liver and kidney tissue and is thought to inhibit protein 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.
Nodularins are potent toxins produced by the cyanobacterium Nodularia spumigena, among others. This aquatic, photosynthetic cyanobacterium forms visible colonies that present as algal blooms in brackish water bodies throughout the world. The late summer blooms of Nodularia spumigena are among the largest cyanobacterial mass occurrences in the world. Cyanobacteria are composed of many toxic substances, most notably of microcystins and nodularins: the two are not easily differentiated. A significant homology of structure and function exists between the two, and microcystins have been studied in greater detail. Because of this, facts from microcystins are often extended to nodularins.
Anthony Edward Walsby, BSc(Birm), PhD(Lond), FRS, is the Emeritus Professor of Microbiology at the School of Biological Sciences, University of Bristol.
Microcystin-LR (MC-LR) is a toxin produced by cyanobacteria. It is the most toxic of the microcystins.
Planktothrix is a diverse genus of filamentous cyanobacteria observed to amass in algal blooms in water ecosystems across the globe. Like all Oscillatoriales, Planktothrix species have no heterocysts and no akinetes. Planktothrix are unique because they have trichomes and contain gas vacuoles unlike typical planktonic organisms. Previously, some species of the taxon were grouped within the genus Oscillatoria, but recent work has defined Planktothrix as its own genus. A tremendous body of work on Planktothrix ecology and physiology has been done by Anthony E. Walsby, and the 55.6 kb microcystin synthetase gene which gives these organisms the ability to synthesize toxins has been sequenced. P. agardhii is an example of a type species of the genus. P. agardhii and P. rubescens are commonly observed in lakes of the Northern Hemisphere where they are known producers of potent hepatotoxins called microcystins.
Cyclamides are a class of oligopeptides produced by cyanobacteria algae strains such as Microcystis aeruginosa. Some of them can be toxic.
Microcystis is a genus of freshwater cyanobacteria that includes the harmful algal bloom-forming Microcystis aeruginosa. Many members of a Microcystis community can produce neurotoxins and hepatotoxins, such as microcystin and cyanopeptolin. Communities are often a mix of toxin-producing and nonproducing isolates.
Microcystis aeruginosa is a species of freshwater cyanobacteria that 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. Microcystis aeruginosa produces numerous congeners of microcystin, with microcystin-LR being the most common. Microcystis blooms have been reported in at least 108 countries, with the production of microcystin noted in at least 79.
Cyanophycinase (EC 3.4.15.6, cyanophycin degrading enzyme, beta-Asp-Arg hydrolysing enzyme, CGPase, CphB, CphE, cyanophycin granule polypeptidase, extracellular CGPase) is an enzyme. It catalyses the following chemical reaction
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 microviridin biosynthesis is much more prevalent, found in many species of Pseudomonadota and Bacteriodota.
George S. Bullerjahn is an American microbiologist, a former Distinguished Research Professor at Bowling Green State University in Ohio. He is the founding director of the Great Lakes Center for Fresh Waters and Human Health. His specialty is microbial ecology; his research has focused on the health of the Laurentian Great Lakes, particularly the harmful algal bloom-forming populations in Lake Erie since the early 2000s.
Susanna Wood is a New Zealand scientist whose research focuses on understanding, protecting and restoring New Zealand's freshwater environments. One of her particular areas of expertise is the ecology, toxin production, and impacts of toxic freshwater cyanobacteria in lakes and rivers. Wood is active in advocating for the incorporation of DNA-based tools such as metabarcoding, genomics and metagenomics for characterising and understanding aquatic ecosystems and investigating the climate and anthropogenic drivers of water quality change in New Zealand lakes. She has consulted for government departments and regional authorities and co-leads a nationwide programme Lakes380 that aims to obtain an overview of the health of New Zealand's lakes using paleoenvironmental reconstructions. Wood is a senior scientist at the Cawthron Institute. She has represented New Zealand in cycling.
References
- 1 2 3 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" (PDF). Aquatic Toxicology. 149: 33–39. doi:10.1016/j.aquatox.2014.01.018. PMID 24561424.
- ↑ Karl Gademann; Cyril Portmann; Judith F. Blom; Michael Zeder; Friedrich Jüttner (2010). "Multiple Toxin Production in the Cyanobacterium Microcystis: Isolation of the Toxic Protease Inhibitor Cyanopeptolin 1020" (PDF). J. Nat. Prod. 73 (5): 980–984. doi:10.1021/np900818c. PMID 20405925.
- ↑ Martin Welker; Hans Von Döhren (2006). "Cyanobacterial peptides – Nature's own combinatorial biosynthesis". FEMS Microbiology Reviews. 30 (4): 530–563. doi: 10.1111/j.1574-6976.2006.00022.x . PMID 16774586.
- ↑ 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 (6): 1089–1104. doi: 10.3390/toxins5061089 . PMC 3717771 . PMID 23744054.
- ↑ Janssen, Elisabeth M.-L. (March 2019). "Cyanobacterial peptides beyond microcystins – A review on co-occurrence, toxicity, and challenges for risk assessment". Water Research. 151: 488–499. doi: 10.1016/j.watres.2018.12.048 . PMID 30641464.
- 1 2 3 Mazur-Marzec, Hanna; Fidor, Anna; Cegłowska, Marta; Wieczerzak, Ewa; Kropidłowska, Magdalena; Goua, Marie; Macaskill, Jenny; Edwards, Christine (26 June 2018). "Cyanopeptolins with Trypsin and Chymotrypsin Inhibitory Activity from the Cyanobacterium Nostoc edaphicum CCNP1411". Marine Drugs. 16 (7): 220. doi: 10.3390/md16070220 . PMC 6070996 . PMID 29949853.
- ↑ "Cyanopeptolin CP1020". pubchem.ncbi.nlm.nih.gov.
- ↑ Rounge, Trine B.; Rohrlack, Thomas; Tooming-Klunderud, Ave; Kristensen, Tom; Jakobsen, Kjetill S. (15 November 2007). "Comparison of Cyanopeptolin Genes in Planktothrix , Microcystis , and Anabaena Strains: Evidence for Independent Evolution within Each Genus". Applied and Environmental Microbiology. 73 (22): 7322–7330. Bibcode:2007ApEnM..73.7322R. doi:10.1128/AEM.01475-07. PMC 2168201 . PMID 17921284.