重金属离子在微囊藻群体形成中的作用机制

The formation, increase, maintenance of Microcystis colony provides a competitive advantage over other phytoplankton species. The formation of Microcystis colony may be impacted by zooplankon grazing and many environmental factors. Heavy metals ions were common pollutants in eutrophic waters, which frequently occurring cyanobacterial blooms. In preliminary studies, we have found the contents of lead, cadmium, chromium, aluminium, ferrum, and manganese of Microcystis were significantly positive with the size of the Microcystis colony in natural waters, and lead(II) could significantly increased the content of bound extracellular polysaccharides and promoted colony formation of Microcystis in the appropriate concentration range. Action rules of main effective heavy metals ions on the colony formation of Microcystis under controlled laboratory conditions will be studied on the basis of making clear the accumulation rule of heavy metals ions by Microcystis. The mechanisms of the action rules above will be studied by analysis of the effects of main effective heavy metals ions on the content and monosaccharide composition of bound extracellular polysaccharides, and the expression of proteins relation to the synthesis of bound extracellular polysaccharides of the algal cells of Microcystis. The results of the present project will play a very important role in making clear the colony formation of Microcystis and revealing the mechanism of outbreaking of Microcystis bloom, and provide abundant scientific reference data for monitoring and controlling of Microcystis bloom, and provide basic scientific data for biotreating of heavy metals contaminated waters.

微囊藻群体的形成、增大和形态的持久维持是微囊藻获得种群优势进而形成水华的前提之一。微囊藻群体的形成可能是浮游动物牧食及环境因子等多种因素共同作用的结果。重金属离子为爆发蓝藻水华的富营养化水体中常见污染物。我们前期研究发现自然水体中微囊藻群体的形态大小与藻体的铅、镉、铬、铝、铁及锰元素含量均呈显著的正相关关系，且实验研究发现Pb2+在一定浓度范围内能够显著提高微囊藻胶鞘多糖的含量，并促进铜绿微囊藻群体的形成。本项目拟在摸清微囊藻对不同类别重金属离子吸附特征的基础上，明确重金属离子在微囊藻群体形成的作用，并通过研究主要效应重金属离子对微囊藻细胞的胶鞘多糖含量、胶鞘多糖单糖组分及与胞外多糖合成相关蛋白表达的影响，阐明重金属离子在微囊藻群体形成中作用机制。研究结果将对摸清微囊藻群体形成机制及揭示微囊藻水华爆发机理具有非常重要的意义，也可为微囊藻水华预警及有效治理提供科学准确的参考数据。

微囊藻群体的形成、增大和形态的持久维持是微囊藻获得种群优势进而形成水华的前提之一。重金属离子为爆发蓝藻水华的富营养化水体中常见污染物。明确重金属离子在微囊藻群体形成的作用，并阐明重金属离子在微囊藻群体形成中作用机制，将对摸清微囊藻群体形成机制及揭示微囊藻水华爆发机理具有非常重要的意义。本项目中我们（1）在建立微囊藻群体细胞精准计数方法基础上发现了自然水体中微囊藻群体对典型重金属离子的具有很强的富集能力，且不同尺寸微囊藻群体细胞对重金属离子的富集能力存在明显差异；另外，我们还发现微囊藻细胞对Cd2+富集过程包括快速吸附和缓慢积累2个阶段；（2）实验生态学条件下开展了重金属离子对微囊藻细胞生长及集聚的影响，结果表明在藻细胞耐受范围内重金属离子可不同程度地促进微囊藻群体形成，其中对微囊藻细胞对Pb2+胁迫的耐受性最强，而Cd2+对促进微囊藻群体的早期形成的作用最为明显；（3）Cd2+与Pb2+可分别不同程度地提高微囊藻细胞胶鞘多糖的含量，且在Cd2+与Pb2+作用下胶鞘多糖含量与微囊藻群体形成及增大表现出极为显著的相关性(P < 0.01)，同时，微囊藻胶鞘多糖的单糖组成对不同浓度的Cd2+、Pb2+胁迫表现明显的差异性，其中葡萄糖所占比例对于重金属离子胁迫作用表现最为敏感，暗示在重金属离子胁迫下微囊藻胶鞘多糖中葡萄糖所占比例可能直接影响微囊藻细胞的耐受力及其群体形成；（4）采用iTRAQ技术分析细胞蛋白表达谱时发现Cd2+可不同程度地通过提高多糖合成、三羧酸循环、光合作用及微囊藻毒素合成途径相关蛋白的表达量来增加藻细胞多糖的产量，进而促进微囊藻群体的形成。