单细胞真核生物四膜虫对汞的甲基化作用及其机理研究

Methylation is an essential process in biogeochemical cycle of mercury (Hg), which significantly enhances both the toxicity and bioavailability of inorganic mercury (IHg). Tetrahymena, located in the bottom of food chain, is a kind of widespread unicellular eukaryotic organism in aquatic environment and plays an important role in bioaccumulation and biomagnification of mercury. Some recent studies have showed the potential of Tetrahymena on methylation of inorganic mercury. Therefore, this project will be focused on the methylation of inorganic mercury by Tetrahymena. Sensitive and accurate method for mercury speciation analysis in cell samples will be developed. The absorption and accumulation of different mercury species in Tetrahymena cells will be investigated. Furthermore, the abilities and mechanisms of different Tetrahymena cells to methylate inorganic mercury will be studied in detail. Based on the experimental results, the roles of Tetrahymena in the transportation and transformation of mercury will also be discussed. It is expected to find new reaction process and mechanism on the methylation of mercury. The results of this project will provide scientific basis for better understand the biogeochemical cycle of mercury.

甲基化是汞生物地球化学循环中的重要过程，可使汞的毒性和生物富集能力显著增加。四膜虫是一类处于食物链底端、水环境中分布广泛的单细胞真核生物，在汞的生物累积和食物链传递中起着重要作用，对汞具有潜在的甲基化作用。本项目拟围绕汞的甲基化这一核心问题，建立细胞中汞的形态分析方法，深入研究不同形态汞在四膜虫体内的吸收累积过程，以及不同四膜虫对汞的甲基化作用和机理，阐明四膜虫在水环境汞迁移转化过程中的作用。项目的完成有望在汞的甲基化过程和机理方面取得新认识，为全面理解汞的生物地球化学循环提供科学依据。

以水环境中广泛分布的单细胞原生生物四膜虫为研究对象，建立了在线测定单个四膜虫中汞含量的capillary single-cell ICP-MS高灵敏度分析方法，为单细胞水平的重金属研究提供了新的分析技术。基于气相色谱-原子荧光联用系统、液相色谱-电感耦合等离子体质谱联用系统以及同位素稀释法，分别建立了四膜虫中甲基汞的分析方法。对五种四膜虫进行了二价汞离子和甲基汞的暴露，系统研究了二价汞离子和甲基汞对四膜虫的不同毒性特征和潜在机制，发现甲基汞对四膜虫的致毒机制主要是破坏四膜虫细胞膜的完整性，而Hg2+可以引起四膜虫体内活性（ROS）的产生进而抑制四膜虫增殖。探讨了五种四膜虫对二价汞离子的甲基化潜力。项目研究结果为深入理解汞的形态转化及生物地球化学循环提供了科学依据，在Analytical Chemistry、Journal of Hazardous Materials等期刊共发表SCI论文8篇，主持撰写出版了《汞的分子转化与长距离传输》专著。