超积累植物根际微生物演替规律及其对重金属活化吸收的影响

The rhizosphere, the region of soil surrounding a plant root, is the site of highest microbial biomass and activity influenced by compounds exuded by the root, has played a significant role in phytoremediation of polluted soil. The principles of microbial succession in the rhizosphere of hyperaccumulators have not been studied extensively, major questions associated with the mechanism by which the effects of microbial succession on heavy metal hyperaccumulating remain unanswered. Sedum alfredii (Crassulaceae), a species native to China, has been characterized as a Zn/Cd cohyperaccumulator and Pb accumulator. To date, studies on the mechanism of metal tolerance and hyperaccumulation of S. alfredii were mainly focused on the uptake and subcellular distribution characteristics, while no information is available about the interactions between rhizosphere microbial succession and heavy metal hyperaccumulating of this plant. In this project, taking into account of the problems in the research of microecology in the rhizosphere of hyperaccumulator, Sedum alfredii and Noccaea caerulescens, both rhizobox and simulated experiments, as well as new techniques like metagenomics, metatranscriptomics, synchrotron radiation techniques, stable isotope tracing, CARD-FISH and ICP-MS were used to (1) investigate the influence of different growth stage and planting cycle on the microbial community structure in the rhizosphere, rhizoplane and endosphere, and then reveal the rhizosphere microbial succession law in the time and space dimension ; (2) examine the effects of plant species, soil type and the level of cadmium pollution on the microbial succession in the rhizosphere of hyperaccumulator; (3) to investigate the influence of rhizosphere microbial community succession on cadmium bioavailability and speciation, and then analyze the relationship between cadmium uptake by plants and succession of the functional microbiome affecting cadmium uptake by hyperaccumulator, as well as assess the mechanism of rhizosphere microbial succession contribute to rhizosphere heavy metal activation and uptake. Results of this project will help to understand the mechanisms by which hyperaccumulator mobilizes and takes up heavy metal from soil and will optimize the management practices for maximum heavy metal phytoextraction, and it is of great importance for protecting soil ecosystem health.

根际是土壤中生命活动最活跃的区域，在污染土壤植物修复中发挥着极为重要的作用。目前，有关重金属超积累植物根际微生物演替规律的报道很少，对根际微生物演替在重金属超积累中的作用机制并不清楚。本项目从根际微生态学入手，以镉超积累植物东南景天、遏蓝菜等为材料，综合应用宏基因组学、宏转录组学、同步辐射、同位素示踪、CARD-FISH等技术，系统研究不同生育期、不同种植周期对超积累植物根际、根表和根内微生物群落结构的影响，揭示根际微生物在时间和空间尺度上的演替规律；研究植物种类、土壤类型、镉污染程度等对超积累植物根际微生物演替的影响；研究根际微生物群落演替对土壤镉生物有效性、形态转化的影响，分析影响镉吸收的功能微生物群落演替与植物镉吸收积累间的关系，揭示根际微生物演替对重金属活化吸收的影响机制，为揭示植物重金属超积累机理，发展根际调控修复技术，提高植物修复效率，保障土壤生态系统健康提供科学依据。

根际是土壤中生命活动最活跃的区域，在污染土壤植物修复中发挥着极为重要的作用。目前，有关重金属超积累植物根际微生物演替规律的报道很少，对根际微生物演替在重金属超积累中的作用机制并不清楚。本项目主要系统研究了不同种植周期内超积累植物不同根系空间微生物群落的变化规律，揭示根际微生物在时间和空间上的演替规律；研究植物种类、土壤类型、镉污染程度等对超积累植物根际微生物演替的影响；研究根际微生物群落演替对土壤镉生物有效性、形态转化和植物镉吸收积累影响，揭示根际微生物演替对重金属活化吸的影响机制。研究发现两种生态型东南景天根系微生物具有明显的时空演替规律，微生物从土壤到根际、根表面和根内多样性逐渐下降。酸杆菌门和芽单胞菌门分类群丰度从土壤到根内丰度明显下降，而变形菌门、拟杆菌门和放线菌门丰度逐步增加。在不同种植周期内，东南景天根际微生物群落表现出可重复的演替特征，根际持续募集α-, β-和γ-变形菌纲、嗜盐菌和热变形菌纲等古菌，它们具有促进重金属超积累的功能。根际微生物共存网络正相互作用比例从79%（第一季）增加到84%（第二季），而非根际土壤则从趋势相反。相比土壤类型（解释了7.1%群落变异）和污染水平（3.5%），植物种类（11%）更能影响超积累植物根系微生物群落结构，且对根内微生物群落（55.4%）的影响是主导性的；根际土壤微生物群落组成则主要受土壤类型和污染水平的影响。根际利用根系分泌物的活跃微生物不受土壤类型和污染程度的影响。根际中携带运动、趋化性和ATP转运蛋白相关基因的微生物丰度显著高于根内。根际和根内耐性微生物群落演替能够改变重金属形态和生物有效性，从而影响植物的吸收和积累。超积累植物地上部内生微生物如链霉菌科、假诺卡氏菌科和根瘤菌科可以通过垂直传递成为新形成根系微生物群落的主要组成，并且促进植物生长和重金属超积累。为揭示植物重金属超积累机理，发展根际调控修复技术，提高植物修复效率，保障土壤生态系统健康提供科学依据。本项目共产出研究论文14篇，其中SCI收录论文13篇，授权发明专利3项，超额完成预期目标。此外，参加学术会议18次，培养研究生6名。