Microcystin composition of an axenic clonal strain of Microcystis viridis and Microcystis viridis-containing waterblooms in Japanese freshwaters

Toxic cyclis heptapeptides (microcystin) in cells of an axenic clonal strain of Microcystis viridis were analyzed quantitatively. Cells from the logarithmic, stationary and death phases of batch culture contained 670, 618 and 372 μg toxic cyclic heptapeptides per g dry cells, respectively. The toxic peptides of the cells from the stationary phase consisted of microcystin RR (65%), microcystin LR (22%), microcystin YR (10%) and microcystin LA (3%). The composition of the toxic peptides changed only slightly through the phases of batch culture. Toxicities and the toxic peptide contents of Microcystis viridis-containing waterblooms in Japanese freshwaters were examined. All samples tested had toxic effects on mice after intraperitoneal injection. The toxic peptides in the samples were composed mainly of microcystin RR (50%) and microcystin LR (30%).