土壤氨氧化微生物对重金属胁迫的响应机制研究

The accumulation of heavy metal in soil will impact the microbial community structure and function. Ammonia-oxidizers are important driver of N cycle in soil, and their responsive mechanism to heavy metal still remains unclear. Many studies have been conducted on the effects of heavy metal on the abundance and community composition of ammonia oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA) based on short-term incubation experiments, which could neglect the sensitivity, resistance and resilience of the ammonia oxidizer groups to the stress of heavy metal. These could lead to an unreasonable evaluation of the toxic effect of heavy metal on soil microorganism. Therefore, the aim of this study is to examine the responses of function and community of ammonia-oxidizers to the stress of heavy metal, basing on the long-term Cu and Ni contaminated fields together with the short-term exposure experiments. The obtained relative parameters will be fitted a dose-response with the concentrations of heavy metal. Then, the dynamic change of the function and community of ammonia-oxidizers in the contaminated soils will be measured using the tests of resistance and resilience, so that understand the process and mechanism of the changes. The results of this study will be helpful to further understand the ecological characters of ammonia-oxidizers in soil, and also provide more reasonable theoretical supports to ecological protection and quality evaluation of agricultural soil.

土壤中重金属的累积会影响土壤微生物的群落结构和功能。氨氧化微生物是土壤N素循环的重要驱动者，但其对重金属胁迫的响应机制尚不清楚。以往的研究主要是基于室内短期培养实验基础上探讨重金属对氨氧化细菌(AOB)和氨氧化古菌(AOA)群落组成和丰度的影响，忽略了土壤中某些氨氧化微生物类群对重金属的敏感性、耐受性以及污染土壤自身的恢复力，从而可能没有合理地评估重金属对土壤微生物的毒性效应。因此，本项目拟以长期重金属Cu和Ni污染的试验田土壤为研究对象，结合短期室内培养实验，研究氨氧化微生物的功能和群落是如何响应重金属的胁迫，从而建立相关参数的剂量-效应关系。在此基础上，通过耐性和恢复力测试试验研究污染土壤氨氧化微生物功能和群落变化动力学，以明确其作用过程和机理。研究的结果将有助于进一步明确土壤氨氧化微生物的生态特性，为农田土壤生态保护和质量评价提供更为准确、合理的依据。

土壤中重金属的累积会影响土壤微生物的群落结构和功能, 微生物也会对重金属胁迫呈现一定的抵抗力和恢复力(环境适应性)，但是我们对其生态机制尚不清楚。本项目以长期重金属污染的农田土壤为研究对象，结合短期室内培养实验，研究土壤微生物的功能和群落是如何响应重金属的胁迫，从而建立相关参数的剂量-效应关系。结果发现，在短时间内重金属(如Cu、As)污染降低了硝化潜势(PNR)，但随着时间的延长，微生物活性有反弹趋势。初次Cu胁迫能够增强土壤微生物对二次Cu胁迫的抵抗力，微生物的功能在胁迫结束后一段时间后表现出了恢复趋势。重金属污染(如Cu、As、Hg)没有改变土壤氨氧化菌丰度，但是明显改变了其群落组成与活性。对于变价重金属Hg而言，微生物受到污染胁迫的同时，可将Hg转化为毒性更大的甲基Hg，从而从排出细胞外，对微生物自身也是一种解毒过程。这些结果对于认识重金属污染胁迫对土壤微生物功能和生物多样性具有重要意义。相关敏感种群具有成为重金属污染指示物种的潜力。因此，该项目的研究成果对于农田土壤质量评价和生态保护都提供了重要数据支持。