耐性细菌与土壤胶体相互作用对重金属植物有效性的影响

Surface interactions between microbes and soil colloids have profound effects on the speciation and plant-availability of heavy metals and subsequent remediation of contaminated soils. However, how these interactions influence phytoextraction of heavy metals ion remains unclear. Previous studies have shown that some resistant bacteria can affect transformation of Cd and increase Cd uptake by Vetiver, an accumulator for Cd. Therefore, we hypothesize that surface interactions between bacteria resistant to Cd and soil colloids can enhance plant-availability of Cd by modifying its transformations. In this study, representative soil types (red soil and calcareous soil and paddy soil) will be collected from southern China and typical soil colloids including kaolinite, montmorillonite and goethite will be used to interact with pre-screened Pb and Cd-resistant bacteria. The effects of surface interactions of soil colloids with Pb and Cd-resistant bacteria on Pb and Cd transformation and plant-availability will be investigated using adsorption-desorption equilibrium, laboratory simulation incubation，model/accumulative/hyperaccumulative plant pot experiment, and fluorescence labeling techniques. The objectives of this project are to: ①ascertain the role and mechanisms of Pb and Cd-resistance bacteria in releasing Pb and Cd from different types of soil colloids and minerals; ②determine the effect of bacteria-mineral interactions on Pb and Cd absorption by model/ accumulative/hyperaccumulative plants in different types of soils and its correlation with chemical speciation of Pb and Cd in soil solution and on the surface of soil minerals; and③ investigate the colonization dynamic characteristics and ecological effects of the Pb and Cd-resistant bacteria in contaminated soils. The results obtained from the proposed research are expected to provide guide and technical support to the phytoremediation of combined ( Pb and Cd ) contaminated soils.

土壤胶体与土壤微生物两大组分的相互作用深刻影响土壤重金属赋存状态和活性，是调控土壤重金属植物有效性的重要因素。但是土壤胶体与耐性细菌相互作用对重金属植物有效性的影响仍然不清楚。前期研究表明耐镉细菌可以改变镉形态，增加重金属富集植物香根草对镉的吸收，推测耐镉细菌与土壤胶体结合可能通过改变镉的形态来增加镉的生物有效性。本项目以筛选出的铅i镉耐性细菌和我国南方主要土类红壤、石灰土和水稻土及其提取的胶体以及高岭石、蒙脱石和针铁矿为材料，采用吸附平衡、模拟培养、模式/富集/超累积植物盆栽试验和荧光标记法开展研究：①探明耐铅镉细菌对不同类型土壤胶体和矿物结合的铅镉离子的释放效应及机制；②明确耐性细菌对不同类型土壤中的模式、富集和超积累植物对铅镉吸收的影响及其与土壤溶液、矿物胶体表面铅镉离子化学形态间的关系；③究明耐性细菌的定殖动态特征和生态效应。研究成果为铅镉污染土壤修复提供理论依据和技术参考。

土壤重金属污染是当今国内外最重要环境问题之一，重金属污染关系到生态安全和人体健康，重金属污染土壤修复和安全利用成为当前国内面临的紧急任务。因此，重金属污染土壤修复理论和技术成为研究热点。由于土壤体系复杂性，一个普遍的共识是，重金属污染土壤修复难！其中最为关键因素是土壤重金属的生物有效性问题。已有的研究表明，土壤胶体与土壤微生物两大组分的相互作用深刻影响土壤重金属赋存状态和活性，是调控土壤重金属植物有效性的重要因素。然而，土壤胶体与耐性细菌相互作用对重金属植物有效性的影响仍然不清楚。本项目前期研究表明耐镉细菌可以改变镉形态，增加重金属富集植物香根草对镉的吸收，推测耐镉细菌与土壤胶体结合可能通过改变镉的形态来增加镉的生物有效性。基于上述背景和基础，立项开展的主要研究内容：① 筛选获得了能耐重金属铅、镉的复合耐性菌株；②探明了铅镉耐性细菌及其与三类土壤胶体复合体对铅、镉离子吸附特征；③探讨耐性细菌对不同类型矿物、土壤胶体结合的重金属离子的形态转化和溶解作用；④探究耐性细菌土壤定殖的动态监测及其生态效应；⑤明确了接种耐性细菌对污染土壤铅镉的活化作用；⑥接种耐性细菌对模式/富集/超积累植物生长及吸收铅镉的影响。获得了重要结果为：① 项目筛选出高耐复合重金属微生物4株，其中2株为细菌、2株为真菌；② 耐性细菌与土壤胶体形成复合体后，能提高对重金属离子的吸附能力；③耐性细菌能促进土壤胶体上重金属形态由无效态向有效态转化，通过改变土壤重金属赋存形态，从而提高重金属生物有效性；④耐性细菌能提高黑麦草、香根草和东南景天生物量，强化植物对重金属的吸收，能增加重金属吸收率为30-45%。.筛选出的耐性菌株是重要的重金属复合耐性的微生物种质资源；探明了耐性细菌与土壤胶体的相互作用对土壤重金属植物有效性有着重要影响；可为铅镉等重金属复合污染土壤的修复技术研发和理论创新提供依据和借鉴。

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