Microcystis toxins

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. 

Zimba, P.V., Khoo, L., Gaunt, P.S., Brittain, S. and Carmichael, W.W. Confirmation of catfish, Ictalurus punctatus (Rafinesque), mortality from Microcystis toxins, J. Fish Dis., 24(1) 41, 2001. 

Sasner JJ, Jr., Ikawa M, Foxall TL (1983) Studies on Aphanizomenon and Microcystis toxins. ACS Symposium Series, vol 262, Sea Food Toxins, American Chemical Society, Washington DC, pp 391—406... 

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). 

Peptide toxins. Of all the toxins produced by freshwater cyanobacteria, the peptide toxins of Microcystis aeruginosa have received the most attention. All research on these peptide toxins indicates they are small, possibly cyclic, with molecular weights estimated at 1200 to 2600 (10,11). Recent work has become more definitive in the estimation of molecular weight and amino acid composition. In 1978 Elleman et al. (12) reported that they had isolated and characterized the peptide toxin of an Australian strain Microcystis which was a pentapeptide with a minimum molecular weight of 654. It consisted of equimolar amounts of alanine, tyrosine, methionine, glutamic and 3-methyl aspartic acid and methylamine. 

Two other research groups have come to similar conclusions about the peptide toxins from Microcystis. Eloff, Siegelman and... 

Three different toxins have been associated with Microcystis aeruginosa. The most common of these is a fast death factor (FDF,... 

Toxins oi Microcystis aeruginosa and Their Hematological and Histopathological Effects... 

The cosmopolitan cyanobacterium Microcystis aeruginosa is frequently the major component of freshwater cyanobacterial blooms. These blooms can cause serious water management problems and are occasionally associated with animal poisoning. The aeruginosa toxins are potent lethal peptides which contain three invariant D-amino acids (Ala, erythro-3-methyl Asp, and Glu), two variant L-amino acids, N-methyl dehydroalanine, and a 3 amino acid (1-3). Multiple toxins have been purified from clonal isolates (1,4). The toxic peptide described in this chapter is denoted toxin-LR using the standard one-letter abbreviations for its two variant amino acids, leucine and arginine. 

D.P. Botes, A.A. Tuinmann, P.L. Wessels, C.C. Viljoen, H. Kruger, D.H. Williams, S. Santikarn, R.J. Smith and S.J. Hammond, The structure of cyanoginosin-LA, a cyclic heptapeptide toxin from the cyanobacterium Microcystis aeruginosa, J. Chem. Soc. Perkin Trans., 1 (1984) 2311-2318. 

W.P. Brooks and G.A. Codd, Immunoassay of hepatotoxic cultures and water blooms of cyanobacteria using Microcystis areuginosa peptide toxin polyclonal antibodies, Environ. Technol. Lett., 9 (1988) 1343-1348. 

I.R. Falconer, M. Dornbusch, G. Moran and S.K. Yeung, Effect of the cyanobacterial (blue-green algal) toxins from Microcystis aeruginosa on isolated enterocytes from the chicken small intestine, Toxicon, 30 (1992) 790-793. 

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. 

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). 

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