Effects of Nitrogen Forms on the Production of Cyanobacterial Toxin Microcystin-LR by an Isolated Microcystis aeruginosa

Abstract

A cyanobacterial strain, which produced high content of microcystin-LR (MC-LR) but no microcystin-RR (MC-RR), was isolated from the hypertrophic Dianchi Lake in China and identified as Microcystis aeruginosa DC-1. Effects of nitrogen containing chemicals and trace elements on the growth and the production of MC-LR by this strain were studied. In the presence of bicine, compared with urea and ammonium, nitrate greatly promoted the growth and the production of MC-LR. However, leucine and arginine, which were the constitutional components in the molecular structure of MC-LR or RR, inhibited the production of MC-LR. Iron and silicon up to 10 mg/L had little effects on the growth of M. aeruginosa DC-1, but the production of MC-LR was apparently enhanced. Under all conditions studied here, only MC-LR but no RR was detected within the cells of M. aeruginosa DC-1. Thus, chemical forms of nitrogen, rather than the usually concerned the total nitrogen, and trace elements played important roles in the production of MC toxins during cyanobacterial blooms.

Keywords:

• Microcystin-LR
• Microcystis aeruginosa DC-1
• Nitrogen; Iron
• Silicon

Acknowledgments

The research was funded by the Chinese National Key Project for Basic Research on the Processes of Lake Eutrophication and the Mechanism of Cyanobacterial Blooming (2002CB412308), Chinese NNSF grant 20177029 and Chinese “863 program” (2002AA601011).