ECOPHYSIOLOGY OF TOXIN-PRODUCING CYANOBACTERIA

Abstract

revista vol 13 nº 2.indd

Ecosystem eutrophication generates conditions which are favorable to the growth of cyanobacterial populations, leading to blooms. Among the 150 known genera of cyanobacteria, 40 include toxin-producing species. Cyanotoxins can be classified based on their chemical structure as cyclic peptides, alkaloids or lypopolyssacharides. However, as a consequence of their letality, the main classes of cyanotoxins are neurotoxins and hepatotoxins. Neurotoxins can lead to death resulting from respiratory arrest. Cyanobacterial blooms of hepatotoxin-producing species are usually more frequent worldwide. The true utility of the toxins to the cyanobacteria that produce them has been controversial among researchers. Some hypotheses claim they may prevent predation by zooplankton, while others claim the substances may chelate heavy metals. Some authors have argued that the toxins may be important for intercellular communication. Moreover, it remains unclear how environmental factors affect the production of cyanotoxins. Most ecophysiological studies have focused on microcystins, as they are the most common cyanotoxins in the world, and evidence from recent studies suggest these substances may be related to the regulation of intracellular inorganic carbon.