Cyanobacteria toxins types

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. 

Freshwater cyanobacteria Microcystis, Oscillatoria, Ana-baena, and Nostoc produce several types of toxins, among which the most commonly detected are the hepatotoxic peptides microcystins. The general structure of the microcystins is cyclo-(D-Ala -X -D-MeAsp -Z -Adda -D-Glu -Mdha ), in which X and Z represent variable L-amino acids, D-MeAsp is D-eryf/iro-p-methylaspartic acid, Mdha is A-methyldehydroalanine, and Adda is the unusual C20 amino acid, (25,35,85,95)-3-amino-9-meth-oxy-2,6,8-trimethyl-10-phenyldeca-4( ),6( )-dienoic acid (Fig. 1). The structural differences in the microcystins mainly depend on the variability of the two L-amino acids (denoted X and Z), and secondarily on the methylation or demethylation of D-MeAsp and/or Mdha. More than 60 microcystins have been isolated from bloom samples and isolated strains of cyanobacteria. 

Freshwater phytoplankton blooms commonly occur in reservoirs, lakes, canals, and ponds under eutrophic and other physicochemical conditions that are favorable for bloom formation. Among the different types of phytoplankton blooms that can occur in freshwater ecosystems, cyanobacterial (blue-green algal) blooms are usually the most undesirable for the following reasons 1) certain species of cyanobacteria can produce toxins that kill aquatic and terrestrial animal life 2) some species of cyanobacteria produce off-flavor compounds that can impart an undesirable taste to cultured fish 3) cyanobacteria are a poor base for... 

The toxins of the cyanobacteria can be classified into categories corresponding to the organs they affect and the type of toxicity they exert. One group encompasses small cyclic peptides (microcystines), which, in relation to their specific transport features, are highly liver-toxic and lead within a few hours to a haemorrhagic shock. Another group consists of neurotoxins, which can be fatal within a few minutes. Anatoxin A binds irreversibly to the nicotinic acetylcholine... 

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