Factors influencing the increase in the proportion of toxigenic cyanobacteria of the genus Microcystis (Chroococcales, Cyanobacteria) in water supply sources

The aim of this review is to summarize current knowledge on the factors influencing the toxigenicity of cyanobacteria of the genus Microcystis and their ability to synthesize hepatotoxic peptides known as microcystins. Environmental factors affecting the ratio of toxigenic to nontoxigenic strains in aquatic ecosystems, as well as the expression levels of genes responsible for microcystin biosynthesis, are analyzed. Particular attention is given to the roles of temperature, light intensity, eutrophication, oxidative stress, and the availability of trace elements. Methods for monitoring toxigenic populations, including molecular biological approaches such as PCR and RT-PCR, are also discussed. Understanding the environmental drivers of toxigenic Microcystis proliferation may contribute to predicting the occurrence of microcystins in drinking water sources and determining optimal sampling periods for toxin monitoring in source waters.