厌氧铁氧化菌介导的土壤-水稻中砷的迁移转化影响机制研究

Arsenic is recognized as carcinogenic; chronic exposure to arsenic results in a wide range of adverse health effects. Paddy rice is efficient at arsenic (As) accumulation due to a combination of the specific As biogeochemical cycle under the flooded environment and the plant physiological characteristics of rice. Rice is the most important contributor to the intake of inorganic As for the general population in China. Some paddy areas in Southern China have been seriously contaminated by As, threatening food safety and human health. Microbe-mediated anaerobic oxidation of ferrous iron plays an important role in arsenic mobilization and detoxification in paddy soil. In this proposal, we focus on the effect of the Fe(II)-oxidizing process on As mobility and transformation, aiming to isolate anaerobic Fe(II)-oxidizing bacteria from arsenic(As) polluted paddy soils or from the rice rhizosphere. The diversity and physiological characteristics of iron oxidizers will be investigated. This research will employ in-site analysis of As contaminated paddy soils and simulation in lab to study As and iron speciation transformation and the relationship between the two processes. The effect of bioaugmenting ferrous iron oxidizers in the rhizosphere on As bioavailability will be investigated. The project will provide a theoretical basis for developing practical measures to reduce As accumulation by rice.

砷污染是一个全球性的环境问题，水稻土生物地球化学过程和水稻特有的生理特性是造成水稻中砷积累的主要原因之一。我国南方水稻产区砷污染现象较严重，危害农产品安全和人体健康。已有研究表明水稻土厌氧铁氧化过程可以耦合砷的迁移转化，但其具体作用机理仍不清楚。本项目以源于水稻土和水稻根际的厌氧亚铁氧化菌为研究对象，探讨其厌氧铁氧化能力与电子供体利用谱（及其与砷形态转化之间的关系）。采用土柱与根际培养箱试验，系统研究不同环境下砷和铁的形态转化规律，分析水稻根际土壤功能微生物种群结构变化关系，探讨通过强化水稻土厌氧铁氧化过程抑制砷对水稻的生物有效性及其具体协同途径和机制，为提出减少水稻砷累积的实用措施提供理论指导。

砷污染是一个全球性的环境问题，本研究针对水稻土厌氧铁氧化过程可以耦合砷的迁移转化，探讨抗砷厌氧铁氧化细菌参与的砷的迁移转化规律及其功能微生物影响机制。主要取得了以下成果：1）分离纯化与鉴定出4株Fe(II)氧化菌，首次发现1株铁氧化细菌具有三价砷氧化的新功能；2）建立了依赖于硝酸盐还原的Fe(II)/As(III)氧化反应体系，阐述了纯培养体系中，Fe(II)/As(III)氧化与硝酸盐还原过程耦联的的微生物-化学过程；3）系统研究了不同浓度硝酸盐对土壤溶液中铁、砷形态转化的影响，揭示淹水水稻土中微生物介导的Fe(II)/As(III)的氧化固定氧化与硝酸盐还原之间的内在联系。本项目研究可为建立基于Fe(II)氧化菌参与砷污染环境的原位修复提供技术支撑。