Cylindrospermopsin and congeners

Cylindrospermopsin (CYN) is a potent cyanotoxin produced by Cylindrospermopsis raciborskii, the first identified producer of CYN, and by several other cyanobacteria genera worldwide. There are five known congeners of the principal toxin 7-(S)-cylindrospermopsin. PKS and NRPS enzymes encoded by cyr gene cluster are involved in CYN synthesis. Different gene organizations, however, have been detected among different CYN producers. There are non-CYN producing strains among the populations of C. raciborskii and other CYN-producing species, some of which exert teratogenicity in the zebrafish embryo model. Moreover, different chemotypes within the same species may occur. CYN affects numerous organs and metabolic pathways. The toxic properties are exhibited by various pathological changes including protein synthesis inhibition, membrane proliferation, fat droplet accumulation, and cell death. Known incidents of human intoxication have been associated with drinking water contaminated by CYN or use of improperly treated water in a dialysis centre. In natural ecosystems, this toxin exhibits toxic influence on a variety of groups of organisms due to its cytotoxic mechanisms. In addition, CYN, being a water-soluble molecule, is bioaccumulated and through trophic transfer it may affect the functioning of both aquatic and terrestrial ecosystems. In this chapter different producers, their distribution and mechanism of toxicity of CYN and congeners are exemplified through results of field and laboratory studies. Moreover, influence on organisms from different trophic levels and whole ecosystems and the biodegradation and biological role of CYN are discussed. Also, different methods of CYN detection are presented.