全球性砷污染日益严重，对环境安全和人类健康构成了潜在的重大威胁。微生物介导下砷的生物转化对砷在环境中的赋存形态、迁移和生物有效性具有重要影响。真核绿藻小球藻（Chlorella vulgaris）广泛存在于土壤、湿地和各类水体中。申请人前期研究证实：小球藻的砷耐受和富集能力极强并具有多种砷代谢途径，但相关的功能基因尚未知晓，其作用机制更是有待明确。本项目运用基因克隆、基因敲除、氨基酸定点突变、蛋白纯化、高效液相色谱-电感耦合等离子体质谱（HPLC-ICP-MS）分析等手段，从小球藻砷转化关键反应入手，系统研究其砷氧化、还原和甲基化酶的作用机制及其生化功能特性。深入探讨小球藻砷代谢的分子生物学机理，阐明环境中真核绿藻与砷的生物地球化学循环的联系。研究结果可为环境介质-污染物-真核藻类相互作用的深入研究开辟新的思路，在实践上可为藻类修复砷污染环境提供科学依据。

Arsenic contamination is increasingly serious worldwide, which impose some potential threats on the environmental safety and human health. Arsenic biotransformation mediated by environmental microorganism plays a crucial role in arsenic speciation, mobility and bioavailability. Eukaryotic green alga (Chlorella vulgaris) exists widely in the soil, wetlands and various aquatic systems. The applicants have confirmed that the alga owned a robust ability in arsenic tolerance and accumulation, and had a variety of arsenic metabolic pathways. Nevertheless, its related functional genes are still unknown, and the action mechanism is needed to be studied. This research keeps an eye on the key arsenic transformation reactions, with the help of analysis methods including gene cloning, gene knockout, amino acid site-directed mutagenesis, protein purification, high performance liquid chromatography coupled with inductively plasma mass spectrometry (HPLC-ICP-MS), demonstrate the functional expression and biochemical characteristics of arsenic oxidase, reductase and transmethylase in Chlorella vulgaris . All of this work will elucidate molecular mechanism of arsenic metabolism in the green alga. Moreover, it will be helpful to illustrate the connection between eukaryotic alga and arsenic biogeochemistry cycle. These results will open up a new way for environment medium-pollutant-eukaryotic alga interaction research and supply some scientific bases for bioremediation of arsenic pollution by algae.