硫酸盐还原菌对红壤水稻土镉形态转化及生物有效性的调控机制

The biogeochemical processes of cadmium in soil are closely related to the sulfur cycle. Sulfate-reducing bacteria play an important role in the soil sulfur cycle, which can reduce sulfate to S2-, and combine with cadmium ions to form precipitates, thereby reducing the bioavailability of cadmium in rice fields. This project sets up a cadmium-contaminated paddy soil simulation experiment to study the effects of different morphological sulfides on the cadmium migration and transformation in soil-rice system. The structural characteristics and abundance changes of sulfate-reducing bacteria and sulfur-oxidizing bacteria in the rhizosphere soil are analyzed using high-throughput sequencing technology, and to clarify the. relationship between sulfur-oxidizing and reducing bacteria populations and morphological transformation of cadmium. Screen sulfate reducing bacteria that effectively reduce the bioavailability of cadmium and explore its physiological and biochemical and molecular mechanisms of sulfate reduction. Taking typical sulfate reducing bacteria as the research object, the mechanism of sulfate reducing bacteria regulating cadmium form transformation and bioavailability of paddy soil in red soil was elucidated from the perspectives of sulfur form transformation, soil physical and chemical properties, soil redox state and root iron plaque. It is expected that the results will provide theoretical basis and technical support for the control of rice soil cadmium pollution and safety production of rice.

土壤镉的生物地球化学过程与硫元素循环密切相关。硫酸盐还原菌在土壤硫循环中发挥着重要作用，其可将硫酸盐还原为S2-，与镉离子结合形成沉淀，从而降低稻田镉的生物有效性。本项目通过设置镉污染水稻土模拟实验，研究不同形态硫化物对土壤-水稻系统镉迁移转化的影响，采用高通量测序技术分析根际土中硫酸盐还原菌和硫氧化菌群的结构特征及丰度变化规律，明确硫氧化还原菌群与镉形态转化之间的关系；筛选高效降低镉生物有效性的硫酸盐还原菌，探究其生理生化和硫酸盐还原分子机制；以典型的硫酸盐还原菌株为研究对象，从硫形态转化、土壤理化性质、土壤氧化还原状态、水稻根表铁膜等多角度，阐明硫酸盐还原菌调控红壤水稻土镉形态转化和生物有效性的机理。预期研究结果将为水稻土壤镉污染控制及稻米安全生产提供理论依据和技术支撑。

重金属污染已经成为危害土壤质量和粮食安全的重要问题。土壤镉的生物地球化学过程与硫元素循环密切相关。土壤镉的生物地球化学过程与硫元素循环密切相关。介导硫酸盐还原过程的硫酸盐还原菌(sulfate-reducing bacteria, SRB)是稻田土壤中重要的功能菌群，在厌氧环境下，其可将硫酸盐还原为S2-，与重金属（如Cd2+、Cu2+、Fe2+）形成硫化物沉淀。本项目通过设置镉污染水稻土模拟实验，研究不同形态硫化物对土壤-水稻系统镉迁移转化的影响，采用高通量测序技术研究根际土中硫酸盐还原菌和硫氧化菌群的结构特征及丰度变化规律，分析硫氧化还原菌（SRB、SOB）的种群分布与镉形态转化之间的关系，阐明硫酸盐还原菌调控土壤镉形态转化及生物有效性的作用机理。研究结果表明，在镉污染土壤中施加硫酸盐底物Na2SO4和Na2SO3能够抑制镉从根部向地上部转运，茎部镉含量显著降低64.8%和83.7%，糙米镉含量显著降低41.5%和48.5%，其作用机理是：施加硫酸盐底物显著影响水稻根际土中的SRB和SOB菌群群落结构，刺激SRB种群数量成数十倍增加，使土壤中的硫酸盐还原活性增强，促进硫酸盐类物质还原为H2S，与土壤中的镉离子形成稳定的镉硫化物，降低土壤可交换态镉含量，促进土壤重金属镉形态的转化，从游离态镉向固定态镉转化，从而降低水稻对镉的吸收转运，显著降低糙米的镉累积。项目研究成果为水稻土壤镉污染控制及稻米安全生产提供理论依据和技术支撑，对于深入理解重金属生物地球化学过程具有重要意义。