根系微生物驱动水稻锑污染物迁移转化的生物地球化学机制

Antimony mining caused farmland contamination is a severe environmental threat in China The elevated antimony concentration in soil leads to excess antimony accumulation in agricultural products. Due to its unique irrigation management methods and hyperaccumulation capability, rice consumption is considered the primary human exposure pathway of antimony. Therefore, understating the antimony accumulation mechanism in rice is necessary for safe agriculture production. Previous literatures demonstrated that rice root exudates can shape the rhizosphere microbial community in response to environmental disturbance, such as elevated metal(loid) concentration. The current project is proposed to study the rice rhizosphere microbial community dynamics and antimony geochemical cycles under different rice growth stages (flooded, drained), which represents different redox conditions. The samples will be collected from the antimony contaminated farmlands neat the major mining areas in south and southwest region in China. We will use stable isotope probing (SIP) technique, combining with metagenomes and binning techniques, to directly link activate microbial community members to the antimony geochemical cycling process. The result of the proposed project will improve our understanding of antimony accumulation process in rice, which is critical for safe agriculture production in China.

我国锑矿的大量开采导致周边的农田污染严重，农作物中累积的锑浓度严重超标。这其中，水稻由于其种植区域与锑矿产区大量重合，独特的淹水种植方式，以及对锑的高累积特性，更易导致锑的累积，因而被WHO认为是锑危害人类健康的首要途径。因此，了解水稻对锑的吸收机制具有重要的科学意义与实际价值。研究表明，水稻会通过根际分泌物调控微生物群落，从而响应环境胁迫。然而，目前我们对水稻根际微生物如何调控锑的吸收仍所知甚少。因此，本项目拟选取我国主要锑矿产区周边污染水稻田作为研究对象，聚焦于水稻不同生长阶段(淹水期、排水期)中，根际微生物对锑污染的调控机制。通过研究水稻根际环境内锑的地球化学循环过程，利用稳定同位素探针（SIP）、宏基因组（metagenome）和单菌基因草图拼装（binning）等先进技术，直接锚定参与锑代谢的关键活性微生物，揭示水稻根际环境内锑的生物地球化学循环过程，为水稻安全生产提供理论基础。

本项目聚焦我国南方常见的锑污染稻田中锑的生物地球化学循环过程，通过对广西、贵州、湖南等多省份污染场地的调查与采样，分析了个场地的金属污染程度与关键元素的含量，并结合微生物群落结构特征，分析了微生物-土壤环境因子间相互作用关系。通过稳定同位素示踪技术，解析了稻田内驱动锑还原过程的关键过程微生物及其机理，并发现了Pseudomonas和Geobacter等类群是水稻土中的锑还原菌；通过宏基因组分析发现Geobacter可能是利用arrA和anrA基因进行锑还原过程；在DNA-SIP技术与宏基因组分箱技术上，与泛基因组分析连用，验证相关代谢潜能在其他近缘微生物存在的普适性，深入研究了水稻对锑的吸收机制具有重要的科学意义与实际价值。