Microcystin production of Microcystis viridis (cyanobacteria) under different culture conditions (original) (raw)

1998, Phycological Research

Toxic cyanobacterium Microcystis viridis was isolated from the eutrophic Dianchi Lake of south-western China. Three microcystins were detected from this strain by high-pressure liquid chromatography. Among them, [Dha 7 ] microcystin-RR is the major component and represents about 70-80% of the total toxins of this strain. We examined its microcystin production pattern in relation to culture conditions such as light intensity, nutrition, temperature, pH and growth phase. Of all the factors examined, light intensity and pH influenced the toxin production much more than other factors. At 25ЊC, a high production of [Dha 7 ] microcystin-RR was obtained at light intensity 15 E s Ϫ1 m Ϫ2 , and both low and high pH (pH 7.0 and pH 9.2) enhanced the yield of microcystin-RR. No strong relationships were found between total toxin and temperature ranging from 15ЊC. The highest production of total toxins was measured in the mid-exponential growth phase and lowest production towards the declining growth phase. Remarkable changes in toxin production and morphology emerged coincidentally following the transfer of nitrogen-deficient cells into fresh MA medium during the time course. These findings may shed light on the correlation between toxin production and morphogenesis of this strain.

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