Persistence and decomposition of hepatotoxic microcystins produced by cyanobacteria in natural environment

Microcystins, the cyclic heptapeptide toxins produced by cyanobacteria such as Microcystis, show tumor-promoting activity through inhibition of protein phosphatases 1 and 2A. They potentially threaten human health and are increasing the worldwide interest in the health risk associated with cyanobacterial toxins. Microcystins are normally considered to be confined within cyanobacterial cells and to enter into the surrounding water after lysis and cell death under field conditions. Five pathways may be considered to contribute to natural routes of detoxification of the microcystins: (1) dilution, (2) adsorption, (3) thermal decomposition aided by temperature and pH, (4) photolysis and (5) biological degradation. In this review, we describe the persistence and decomposition of microcystins under the conditions mentioned above and discuss the fate of the toxins in the natural environment.