Microcystis microcystins

In the Slimmer of 1989, Rutland Water, the largest man-made lake in Western Europe and which supplies potable water to approximately 500 000 people in the East of England, contained a heavy bloom of Microcystis aeruginosa. By the end of the summer, a number of sheep and dogs had died after drinking from the bloom and concentrated scum. Analysis revealed that the cyanobacterial bloom material was toxic to laboratory mice, and that rumen contents from a poisoned sheep contained fivemicrocystin variants.Microcystins were detected in waters used for recreation in Australia at concentrations greater than 1 mg per... 

Lehman PW, Boyer G, Satchwell M, Waller S (2008) The influence of environmental conditions on the seasonal variation of Microcystis cell density and microcystins concentration in San Erancisco Estuary. Hydrobiologia 600 187-204... 

Figure 8. Left The cyclic heptapeptide hepatotoxin microcystin-LA (cyanoginosin-LA) produced by the colonial cyanobacterium Microcystis aeruginosa strain WR-70 (UV-010). MW = 909. Right The cyclic heptapeptide hepatotoxin microcystin-LR (cyanoginosin-LR) produced by a waterbloom of the colonial cyanobacterium Microcystis aeruginosa collected in Lake Akersvatn, Norway, 1984-85 MW=994, 69J1).

Rapid-acting cytotoxin that disrupts cell membranes in the liver (hepatoxin) causing an accumulation of blood in the liver. It is the most toxic of the Microcystins. It is a solid obtained from freshwater blue-green cyanobacteria (Microcystis aeruginosa, Microcystis cyanea). It is heat stable and water soluble. Aqueous solutions are "probably stable" and resistant to chlorine at 100 ppm. It is also soluble in alcohol and acetone. 

Significant concentrations of cyanotoxins have been found to accumulate in the tissues of macroinvertebrates such as mollusks and crustaceans, presenting an indirect route of exposure for invertebrates, fish, and aquatic mammals at higher trophic levels (Negri and Jones 1995). In natural systems, mortality among benthic invertebrate herbivores is probably low because most bloom-forming bacteria are planktonic and only periodically come into contact with the benthos. Nevertheless, Kotak et al. (1996) determined that enhanced mortality of snails at the end of a bloom cycle in Canadian lakes was due to consumption of Microcystis cells that had formed a scum on the surface of macrophytes. Oberemm et al. (1999) found that aqueous microcystins, saxitoxins, and anatoxin-a all resulted in developmental delays in fish and salamander embryos. Interestingly, more severe malformations and enhanced mortality were observed when larvae were exposed to crude cyanobacterial extracts than to pure toxins applied at natural concentrations (Oberemm et al. 1999). 

The main genera responsible for freshwater toxic blooms are Microcystis, Anabaena, Aphanizomenon and Oscillatoria. Toxins produced include 1. anatoxins, alkaloids and peptides of Anabaena 2. the peptide microcystin and related peptides of Microcystis 3. aphantoxins, compounds of Aphanizomenon with properties similar to some paralytic shellfish poisons. Properties of Oscillatoria toxin suggest they are peptides similar to those of Microcystis. Microcystis toxins are peptides (M.W. approx. 1200) which contain three invariant D-amino acids, alanine, erythro-3-methyl aspartic and glutamic acids, two variant L-amino acids, N-methyl dehydro alanine and a 3-amino acid. Individual toxic strains have one or more multiples of this peptide toxin. The one anatoxin characterized is a bicylic secondary amine called anatoxin-a (M.W. 165). The aphantoxin isolated in our laboratory contains two main toxic fractions. On TLC and HPLC the fractions have the same characteristics as saxitoxin and neosaxitoxin. 

G.A. Codd, J.S. Metcalf and A.B. Kenneth, Retention of Microcystis aeruginosa and microcystin by salad lettuce (Lactuca sativa) after spray irrigation with water containing cyanobacteria, Toxicon, 37 (1999) 1181-1185. 

Cyanobacterial (Blue-Green Bacteria) Toxins. Cyanobacterial poisonings were first recognized in the late 1800s. Human poisonings are rare however, kills of livestock, other mammals, birds, fish, and aquatic invertebrates are common. It is caused by a variety of biotoxins and cytotoxins, including anatoxin, microcystin, and nodularin produced by several species of cyanobacteria, including Anabaena, Aphanizomenon, Nodularia, Oscillatoria, and Microcystis. The main contamination problems include all eutrophic freshwater rivers, lakes, and streams. 

T Nishizawa, M Asayama, K Fujii, K Herada, M Shirai. Genetic analysis of the peptide synthetase genes for the cyclic heptapeptide microcystin in Microcystis spp. J Biochem (Tokyo) 126 520-529, 1999. 

The aromatic p-amino acid Adda 74 [114] is a substructure of several cyclopeptides from cyanobacteria, i.e. the microcystins 86 and nodularin 85. More than 60 microcystin and nodularin homologs have already been isolated from the genera Microcystis, Anabama, and Oscillatoria (microcystins) as well as Nodularia (nodularins). A multitude of literature is available on the biosynthesis and biological activity of these hepatotoxins, which can constitute a serious health hazard in fresh water [135]. 

Microcystins LR RR] Microcystis aeruginosa (blue-green PP1 (at InM), PP2A... 

In Japan, the first detection of AN and its degradation product, epoxy-AN, have been reported (Park et al. 1993). This was also the first study to show that Microcystis could produce both AN and microcystins. The predominant species were Anabanea and Planktothrix with toxin concentrations in the range 0.4-16 pg AN/g. In addition, AN, HMAN, and a new compound, hydroxy-HMAN, were isolated from Raphidiopsis mediterranea in Japan (Namikoshi et al. 2003 Watanabe et al. 2003). AN was also found in four of 26 samples from Korean lakes, collected during 1992-1995 (Park etal. 1998). 

Lawton, L.A., Edwards, C., Beattie, K.A., Pleasance, S., Dear, G.J., and Codd, G.A., 1995. Isolation and charaterization of microcystins from laboratory cultures and environmental samples of Microcystis aeruginosa and from an associated animal toxicosis. Natural Toxins 3 50-57. 

Namikoshi, M., Rinehart, K.L., Sakai, R., Stotts, R.R., Dahlem, A.M., Beasley, V.R., Carmichael, W.W., and Evans, W.R. 1992. Identification of 12 hepatotoxins from a Homer Lake bloom of the cyanobacteria A/icrocyshs aeruginosa. Microcystis viridis, and Microcystis wesenbergii Nine new microcystins. Journal Organic Chemistry 57 866-872. 

Microcystins and Nodularins Mieroeystins (MC) are widely distributed eyanotoxins, and have often been implicated in aeeidental human and animal poisonings. They are produeed by several genera, including the planktonic Microcystis, Planktothrix, Anabaena species, and the benthic Oscillatoria. Nodularins are only produced by the species Nodularia spumigena, whieh occurs in brackish waters, essentially in the Baltie Sea, Australia, and New Zealand. 

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