铜绿微囊藻的生长及产毒条件研究

Study on Growth and Toxin Production of Microcystis aeraginosa Strain Under Different Conditions

目的研究温度、光照、氮磷浓度对铜绿微囊藻的生长及微囊藻毒素LR产生的影响。方法采用BG-11为培养基,通过计数藻细胞来反映其生长特性,用高效液相色谱法测定微囊藻毒素LR产量,观察不同温度(20～35℃)、光照(2000～5000lx)、氮(71.4～1300.0μmol/L)、磷(1.43～71.40μmol/L)浓度对铜绿微囊藻的生长及微囊藻毒素LR产生的影响。结果铜绿微囊藻在25℃和3000lx时生长最快,但细胞内产毒量却分别在20℃和5000lx时达到最大值;在固定磷浓度(6.50μmol/L)的培养条件下,铜绿微囊藻细胞数和毒素产量均随氮浓度的升高而增加,在650.0μmol/L时达到最高峰,继续增高则有抑制作用;在固定氮浓度的培养条件下(71.4μmol/L),磷浓度为1.43μmol/L时细胞生长较慢,浓度达到6.50μmol/L时细胞生长加速,但浓度进一步加大,藻细胞生长曲线无明显变化,产毒量也未见明显不同;同时,微囊藻毒素-LR浓度与藻细胞数和叶绿素含量之间均存在明显的正相关关系。结论铜绿微囊藻的最佳生长条件并不等同于其最佳产毒条件;磷是一种限制性营养因子,较低浓度就可满足藻类生长及产毒需要;适合铜绿微囊藻生长和产毒的氮磷比是100∶1(原子数比);可通过细胞计数或测定叶绿素含量来预测水中微囊藻毒素-LR的总浓度。

Objective To study the impact of temperature, light, nitrogen and phosphorus on growth and microcystin-LR production of Microcystis aeraginosa strain under laboratory conditions. Methods M.aeraginosa strain was cultivated in BG-11 medium. Growth was determined by counting cell, while microcystin-LR was analyzed by high-performance liquid chromatography.Results M.aeraginosa strain had a biggest growth rate at temperature of 25 ℃ and light intensity of 3 000 lx, while microcystin-LR production contents reached maximum at 20 ℃ and 5 000 lx respectively. Under the phosphorus-fixed condition, M. aeraginosa amount and mircrocystin-LR content increased by nitrogen concentration and reached the peak when the nitrogen concentration was 650.0 μmol/L. But higher concentration of nitrogen could probably restrain the cell growth and toxin production. Under the nitrogen-fixed condition, M. aeraginosa strain grew slowly at phosphorus concentration of 1.43 μmol/L, but had a higher growth rate when phosphorus concentration was 6.50μmol/L No significant change was found with the increase of phosphorus concentration. And almost similar contents of microcystin-LR produced by M. aeraginosa were observed at different phosphorus concentrations. Positive correlations between total microcystin-LR concentrations and chlorophyll-a contents and M. aeraginosa cell densities were found. Conclusion The optimum conditions for growth and toxin production of M. aeraginosa are not the same. Phosphorus is a probable limitation nutrient factor, and a low concentration will satisfy the growth and toxin production ofM. aeraginos. The N ：P atomic ratio at 100：1 was determined as the optimum for growth and toxin production. The total microcystin-LR concentration can be forecasted by M. aeraginosa cell density or chlorophyll-a content.