First report of microcystin production in Microcystis smithii Komarek and Anagnostidis （Cyanobacteria） from a water bloom in Eastern China

A water bloom sample collected from Lake Dishui in Shanghai was characterized. The morphological identification showed that Micorcystis wesenbergii and Micorcystis smithii were the main component of the bloom. Five strains of M. smithii were successfully isolated. Their 16S rRNA gene sequences based phylogenetic tree showed that the five strains of M. smithii intermixed with strains of other morphospecies in Microcystis. A fragment of mcy gene encoding for microcystin synthetase was detected in one of the five M. smithii strains （CHAB 2183）, indicating its potential of microcystin production. High performance liquid chromatography analysis confirmed M. smithii CHAB 2183 to produce microcystin-RR as 1550 μg per gram dry weight cells. The present investigation, for the first time, reported the isolated strains of M. smithii and microcystin production from M. smithii.