稻田异化硝酸盐还原为铵微生物功能群对不同施肥措施和作物生长的响应

Increasing evidence indicated that microbial mediated Dissimilatory Nitrate Reduction to Ammonia (DNRA) was a probably important factor, which inhibited nitrogen loss in paddy soils. However, little has been known about the mechanism by which the environmental factors modulate the functional DNRA microbial community. The present proposal will employ an experimental paddy field in Wuxue for the study. Soil properties/pore water chemistry, nitrate reducing potential and DNRA activity will be determined. High-throughput sequencing of the nrfA genes will be utilized to investigate the structure of DNRA bacterial community. The functional genes that represent nitrate reducers and DNRA bacteria will be quantitatively measured at both DNA and transcriptional levels. Several multivariable analysis methods will be employed to decipher the linkages among DNRA microbial community structure, function, fertilization regimes, and the plant growing stages, as well as the asscociated changing factors. This study will get insight into the molecular ecological mechanism by which the paddy soil DNRA microbial community responses to some environmental factors. The results from this study will probably deepen our understanding of the mechanism of paddy soil nitrogen cycle, and provide new theoretical evidence to guide our soil management.

越来越多的研究暗示微生物介导的异化硝酸盐还原为铵作用可能是抑制稻田氮素损失的关键因素之一。然而我们对稻田环境异化硝酸盐还原为铵微生物功能群受环境因子调控的规律知之甚少。本课题以武穴地区一水稻长期定位实验田作为研究对象，一方面测定稻田土壤理化性质/孔隙水化学参数、硝酸盐还原和异化硝酸盐还原为铵的活性；另一方面，通过对nrfA基因高通量测序，对稻田异化硝酸盐还原为铵微生物群落进行研究。此外，对16S rRNA基因和涉及硝酸盐还原、异化硝酸盐还原为铵的关键功能基因narG、napA、nrfA在DNA和RNA水平定量。利用多种多变量分析方法量化稻田异化硝酸盐还原为铵微生物功能群对长期施肥措施、分蘖期追肥、水稻生育期及相关环境因子变化响应的规律，初步揭示其结构、功能对稻田部分环境因子响应的分子生态学机制。这将加深我们对稻田氮循环机制的理解，同时可为田间管理、农田质量评价提供科学依据。

本课题通过对不同施肥处理或不同背景肥力的农田生态系统的异化硝酸盐还原到铵（Dissimilatory nitrate reduction to ammonia）微生物和细菌群落进行研究，发现有机或无机施肥措施对DNRA微生物α多样性影响相对较小，对其物种组成影响大。对DNRA微生物群落产生影响的关键因子为土壤有机碳含量、总氮和pH。而在施用含碳材料作为改良剂的土壤中，亚硝酸盐氧化菌中亚硝化杆菌主要受pH影响，硝化螺菌主要受pH值、全氮和NH4+调控。天然高低稻田的群落结构组成上却差异显著。高产田的微生物网络具有较高的连通性，可能有助于水稻成熟期招募更多的微生物来执行有机物分解、硫酸盐/铁还原、氮的转化和甲烷氧化等功能。在低产田中施用氮肥将有助于招募能执行类似于高产田中类似生态过程的微生物。此外发现环境因子对蛭弧菌和类蛭弧菌捕食者存在至下而上调控—土壤理化性质调控被捕食者群落，被捕食者的多样性决定了上层捕食者的数量。