溶磷菌胞外分泌物对土壤镉的配位活化机理

Our previous studies and related reports show that the use of phosphate solubilizing bacteria to enhance the extraction of cadmium from soil by hyperaccumulating plant is an effective way to repair the cadmium pollution in slight acidic and neutral farmland. As a plant growth promoting bacteria, phosphate solubilizing bacteria can not only promote the growth of hyperaccumulating plants, but also promote the dissolution of cadmium in soil and the uptake of cadmium by plant. Coordination play a very important role in the mobilization of cadmium in soils except acid dissolution by phosphate solubilizing bacteria. However, it is not clear that the specific coordination process and coordination mechanism. This project through the isolation and identy the speciation of cadmium, iron, and aluminum complexes in the extracellular solution after mobilization of cadmium in soil, to ascertain what extracellular secretion have strong coordination function with cadmium and carrier fixed cadmium, what ligands are involved in coordination, what metal are these ligands coordinated to, and what substances are formed after these ligands are coordinated? It will elaborate the role of various secretions in the mobilization of different forms soil cadmium, and reveal coordination mobilizing mechanism of phosphate solubilizing bacteria on soil cadmium, to provide scientific basis for plant growth promoting bacteria strengthening the remediation of cadmium contaminated soil and for the research and development of high efficient cadmium mobilizing phosphate solubilizing bacteria.

我们的前期研究及相关报道表明，利用溶磷菌强化超富集植物萃取土壤镉，是修复弱酸性和中性土壤农田镉污染的有效途径。作为根际促生菌，溶磷菌不仅对修复植物有促生效果，还能促进土壤镉活化、增强植物对镉的吸收。溶磷菌对土壤镉的活化除了通过酸溶作用外，配位作用也起非常重要的作用。但是，具体配位过程及配位机制尚不清楚。本项目拟通过分离和鉴定溶磷菌活化土壤镉后胞外溶液中镉及铁/铝等金属配合物的形态，探知哪些胞外分泌物对土壤镉及镉的固定载体具有强配位功能，弄清什么配体参与了配位？跟什么物质配位？配位后生成了什么物质形态？从而阐明各种胞外分泌物在配位活化不同形态土壤镉时的作用，揭示溶磷菌胞外分泌物活化土壤镉的配位作用机理，为开发高效溶镉溶磷菌强化超富集植物修复镉污染土壤提供科学依据。

溶磷菌对土壤镉的活化除了通过酸溶作用外，配位作用也起非常重要的作用。本项目通过代谢组学分析，确定了溶磷菌分泌的铁载体是配位作用活化土壤镉的主要成份。通过合成铁载体类似物，研究其与镉及镉的固定载体中铁、铝的配位结构特性，发现了铁载体主要通过氮/氧多齿配位模式以1:2（镉:配体）形式配位镉，或以1:2:6（镉:铝/铁:配体）形式同时配位镉、铝/铁。揭示了溶磷菌胞外分泌物活化土壤镉的配位作用机理。