典型区域水稻耕作层土壤"溶解性有机质与地杆菌属铁呼吸菌"的多样性特征及其生态关联性

Soil dissolved organic matter (DOM) is an important electron shuttle for Geobacter-related dissimilatory iron-reducing bacteria (G.-FeRB) in paddy field ecosystem. The co-existence of soil DOM and the G.-FeRB complex plays a important role in regulating the bioavailability of heavy metals and nutrients, the biodegradation of organic pollutants, and the generation of greenhouse gases. However, due to the structural complexity of DOM chemistry and diversity of the G.-FeRB community, the ecological linkages between soil DOM and G.-FeRB over a broad spatial range is poorly understood. This knowledge gap hinders the development of cost-effective strategies for fortifying the health of the paddy field ecosystem. This proposal will explore three groups of paddy field soil with significant differences in geographical features, climate condition, and soil biogeochemistry across China, including the HongHe plateau terrace paddy fields (Vertical climate) in YuNang province, the paddy fields around the TaiHu basin (Subtropical climate), and the paddy fields in SanJiang plain in HeRongJiang province (Temperate climate). Topsoil from these ecosystems will be sampled during the blooming phase of rice tilling. The main goals of this proposal are: 1) to understand the molecular diversity of DOM (or chemodiversity) and to illustrate the geographic variability and spatial features of soil DOM chemodiversity; 2) to identify the strain specific diversity of the G.-FeRB populations and ecological functions using Shannon entropy oligotyping, and to determine the biogeographic structure of these populations; 3) to calculate the space-dependent ecological linkages among the chemodiversity of DOM, diversity of G.-FeRB, and environmental parameters by using local similarity correlations and network analysis, so as to reveal the correlative interactions that define local and national-scale biogeographic structure; 4) to discuss the optimal strategies for soil DOM dynamic and G.-FeRB activities, so as to develop proposals to enhance the health of the paddy field ecosystem. The purpose of this proposal is to provide new insights into the co-occurrence of soil DOM and G.-FeRB for improving regional agricultural and ecological sustainability.

水稻土壤地杆菌属铁呼吸菌（G.-FeRB）的能量代谢常需要溶解性有机质（DOM）作为电子穿梭体来协助完成，并调控金属与养分有效性、有机污染物降解及温室气体产生等过程。由于土壤DOM分子组分的复杂性与G.-FeRB菌群的多样性，两者是否存在规律性的生态关联性尚不清楚。因此，本项目选取云南哈尼梯田、环太湖、东北三江平原等地理与人类活动显著差异的水稻区，重点开展：1）基于超高分辨质谱（FT-ICR-MS）技术，在分子层面阐述土壤DOM化学多样性（Chemodiversity）及其区域差异化特征；2）基于Oligotype配型识别，深入到亚种水平揭示土壤G.-FeRB菌群结构与功能多样性及其区域差异化特征；3）基于局部相似-网络分析，阐明“G.-FeRB菌与DOM”之间多元化、趋势性及相对强度的复杂生态关联性及其区域差异化规律。本项目可从G.-FeRB菌与DOM协同调控的机理服务绿色高效农业生产。

微生物介导了水稻土中的各种生物地球化学过程，溶解性有机质(DOM)在水稻土的生物地球化学过程中也扮演着重要角色。水稻土壤地杆菌属异化铁还原菌(G.-FeRB)需要溶解性有机质(DOM)作为电子穿梭体完成能量代谢，并调控重金属与养分有效性、污染物降解及温室气体产生等过程。据此，本研究选取我国三江平原、两湖平原、太湖平原和哈尼梯田四个典型的水稻种植区，重点开展：1）基于化学多样性(Chemodiversity)原理揭示DOM电子转移潜力及其空间变化特征；2）基于Oligotype配型阐述G.-FeRB菌深入到亚种水平的种群与功能多样性特征及其空间变化趋势；3）基于局部相似-网络分析，可视化地阐明土壤“G.-FeRB菌与DOM”在地理尺度上生态关联性的多元化特征、指向性趋势、及强弱度水平。研究发现：1）水稻土微生物与非水稻土相比具有显著更低α多样性(丰富度、多样性和均匀度)，水稻土微生物共现网络中的大多数相互关系都是独特的；同时，水稻土微生物共现或互斥关系具有显著的区域性特征；2）DOM分子组成与微生物群落一样，也具有显著的地理分布模式；且该模式亦由地理距离、月均降水、pH、年均温度、海拔高度等环境因子，以及微生物群落组成特征所驱动，DOM分子组成的β多样性特征也可解释最多的微生物β多样性变化；3）DOM分子中，多肽、糖类和不饱和脂肪族化合物分子丰度的增加，以及多酚和多环芳烃化合物分子丰度的减少，与一些微生物(如属Syntrophobacterales、Thermoleophilia、Geobacter，所有产甲烷菌属等)的丰度变化显著相关。这些DOM分子的变化还与微生物代谢通路(如厌氧固碳、糖酵解、木质素分解、发酵和产甲烷等)的变化相关。本研究所得结果或结论为深入揭示长期人类活动影响下的土壤微生物群落的构建规律，以及微生物群落与DOM分子组成的生态关联本质具有重要科学意义。