Toxins of cyanobacteria

Camacho FA, Thacker RW (2006) Aniphipod herbivory on the freshwater cyanobacterium Lyngbya wollei. chemical stimulants and morphological defenses. Limnol Oceanogr 51 1870-1875 Carmichael WW (1994) The toxins of cyanobacteria. Sci Am 2780 78-86 Carmichael WW (2001) Health effects of toxin-producing cyanobacteria the cyanoHABs . Hum Ecol Risk Assess 7 1393-1407... 

BornerT, New bioactive compounds. Toxins of cyanobacteria, Biologic in Unserer... 

W.W. Carmichael, V. Beasley, D.L. Bunner, J.N. Eloff, I.R. Falconer, P. Gorham, K.-I. Harada, T. Krishnamurthy, Y. Min-Juan, R.E. Moore, K. Rinehart, M. Runnegar, O.M. Skulberg and M. Watanabe, Naming of cyclic heptapeptide toxins of cyanobacteria (blue-green algae), Toxicon, 26 (1988) 971-973. 

Carmichael, W.W, Beasley, V, Bunner, D.L., Eloff, IN., Ealconer, I., Gorham, P, Harada, K.-L, Krishnamurthy T, Min-Juan, Y, Moore, R.E., Rinehart, K., Runnegar, M., Skulberg, O.M., and Watanabe, M. 1988. Naming of cyclic heptapeptide toxins of cyanobacteria (blue-green algae). Toxicon 26 971-973. 

Carmichael, W.W. et al., Naming of cychc heptapeptide toxins of cyanobacteria (blue-green algae),... 

Carmichael WW. The toxins of Cyanobacteria. Sci Am 1994 270 78-86. Nishiwaki Matsushima R, Ohra T, Nishiwaki S, Suganuma M, Kohyama K, Ishikawa T, Carmichael WW, Fujiki H. Liver tumor promotion by the cyanobacteria 1 cyclic peptide toxin mkrocystin-LR. J Cancer Res Clin Oncol 1992 118 420-424. 

Not all cyanobacterial blooms and scums contain detectable levels of toxins. Indeed, the incidence of toxicity detection by mouse bioassay, and toxin detection by HPLC among environmental samples, ranges from about 40% to However, in view of this high occurrence, it is the policy of regulatory authorities and water supply operators in some countries to assume that blooms of cyanobacteria are toxic until tested and found to be otherwise. In the absence of available analytical facilities or expertise or for logistical reasons, this precautionary principle should be regarded as sensible and prudent. 

Other toxins that show low lethal toxicity to laboratory test animals include lipopolysaccharide endotoxin produced as part of the cell wall by all cyanobacteria 11) and certain toxins of some cyanobacteria suspected of causing contact irritation in recreational water supplies 4,12 Carmichael and Codd, unpublished results). 

In vitro studies on isolated cells including hepatocytes, erythrocytes, fibroblasts, and alveolar cells continue to demonstrate the specificity of action that these toxins have for liver cells (83,86,93). This specificity has led Aune and Berg (94) to use isolated rat hepatocytes as a screen for detecting hepatotoxic waterblooms of cyanobacteria. 

Acute poisoning of humans by freshwater cyanobacteria as occurs with paralytic shellfish poisoning, while reported, has never been confirmed. Humans are probably just as susceptible as pets, livestock, or wildlife but people naturally avoid contact with heavy waterblooms of cyanobacteria. In addition, there are no known vectors, like shellfish, to concentrate toxins from cyanobacteria into the human food chain. Susceptibility of humans to cyanobacteria toxins is supported mostly by indirect evidence. In many of these cases, however, if a more thorough epidemiological study had been possible these cases probably would have shown direct evidence for toxicity. 

Oberemm A, Becker J, Codd GA, Steinberg C (1999) Effects of cyanobacterial toxins and aqueous crude extracts of cyanobacteria on the development of fish and amphibians. Environ Toxicol 14 77-88... 

FFepatotoxins are the most commonly encountered toxins involving cyanobacteria, that include the cyclic peptides microcystin and nodularin (Fig. 4). Microcystins are cyclic seven amino acid peptides, and nodularins are cyclic five amino acid peptides. Over 50 different variants of microcystin have been isolated. 

Throughout the world, there are many different types of innocuous phytoplankton that can inhabit freshwater ecosystems. However, in some of these ecosystems, certain species of cyanobacteria (blue-green algae) are highly undesirable due to their production of toxins or odorous compounds. 

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. 

Other Peptide Toxin Producing Cyanobacteria. No other cyanobacteria genera have been analyzed for the presence of toxic peptides. Based on toxicity signs however it is thought that peptide toxins are present in certain isolates of Anabaena flos-aquae (J) and Oscillatorla agardhil (9,17). 

Two other suspected alkaloid producing cyanobacteria strains, Anabaena flos-aquae NRC-525-17 and Aphanizomenon flos-aquae NH-5, are now being studied. The toxin of flos-aquae NRC-525-17 (anatoxin-a(s)) is thought to have CNS stimulating properties (7) and that of Aph. flos-aquae NH-5 (aphantoxin) is thought to produce the paralytic shellfish poisons saxitoxin and neosaxitoxin (Fig. 1)... 

Cyanobacterial toxins (both marine and freshwater) are functionally and chemically a diverse group of secondary chemicals. They show structure and function similarities to higher plant and algal toxins. Of particular importance to this publication is the production of toxins which appear to be identical with saxitoxin and neosaxitoxin. Since these are the primary toxins involved in cases of paralytic shellfish poisons, these aphantoxins could be a source of PSP standards and the study of their production by Aphanizomenon can provide information on the biosynthesis of PSP s. The cyanobacteria toxins have not received extensive attention since they have fewer vectors by which they come in contact with humans. As freshwater supplies become more eutrophicated and as cyanobacteria are increasingly used as a source of single cell protein toxic cyanobacteria will have increased importance (39). The study of these cyanobacterial toxins can contribute to a better understanding of seafood poisons. 

Certain strains of cyanobacteria produce toxins. These cyanobacterial toxins can be classified according to their chemical structure or their toxicity. Table 16.1 summarises the characteristics of the main cyanobacterial toxins. Depending on the chemical structure, there are cyclic peptides, alkaloids and lipopolysaccharides. According to the toxic effects, they are classified as ... 

The developed biosensor should be, in principle, applicable to any sample suspicious of containing microcystins. This includes water samples, cyanobacterial cells and infected organisms. Whereas water samples could be directly applied to the biosensor, specific extraction protocols are required for the detection of the toxin in cyanobacteria and other organisms. In all the cases, matrix effects should be evaluated. 

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