"Cyanobacterial mass development – positive and negative effects"

Stephan Pflugmacher
Leibniz Institute of Freshwater Ecologyand Inland Fisheries, Biochemical Regulation, Müggelseedamm 301, 12587 Berlin, Germany,
Pflugmacher@IGB-Berlin.de

Many of the bloom forming cyanobacteria are known to produce different types of secondary metabolites. Research in the past years has shown that cyanobacterial secondary metabolites can have positive as well as negative effects. Most of the positive effects are based in the field of pharmacology. Under the positive effects some secondary metabolites can have anti-HIV effects, they can act as protease inhibitors, they can have antimicrobial activity, they can have anti cancer effects and even they can act as prevention for malaria.
But cyanobacterial secondary metabolites are also known to have adverse effects on mammals, birds, fish, mussels and plants and are being increasingly recognized as a potent stress and health hazard factor in the aquatic as well as the terrestrial ecosystem. Some of them being toxic and are therefore categorized as hepatotoxins, neurotoxins and cytotoxins. A wide range of aquatic organisms are directly exposed to cyanobacterial toxins, which cause diverse effects. Exposure of aquatic organisms may occur both orally by uptake of toxin-containing cells as food, or through the surface tissues of organisms submersed in water contaminated with toxin. The possible uptake routes of toxins in organisms as well as bioaccumulation of toxin in tissues will be discussed. Furthermore effects detected such as feeding inhibition, influence of toxin on germination and growth, inhibition of photosynthesis, inhibition on protein phosphatase or the promotion of oxidative stress response.
Studies on the metabolism of cyanobacterial toxins in animals and plants are rare. Today the more or less complete detoxification pathway of microcystin in different animals and plants is known starting always with the conjugation to glutathione catalyzed by the glutathione S-transferase. The formed glutathione conjugate is further processed and in case of animals excreted, in case of plants transported to the vacuoles or used as cell wall components. In this lecture the basic information on biotransformation in general, the enzymes working in biotransformation reactions, the three phases of detoxification including the “green liver” concept and examples for the detoxification of cyanobacterial toxins in different organisms will be given.

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