土壤产电信号及其指示土壤重金属污染的微生物机制

Soil has electrogenic bacteria, which can generate electrical power in microbial fuel cells (MFCs). The generated voltage or current by soil were regarded as electrical signals, which could be used as indicators of heavy metal pollution in soil. The electrical signals would become weaker with more severe heavy metal pollution. The process of indication has great advantages in that it is continuous and in real time without energy input and pollutants output. However, it is still unclear of the microbial mechanisms that the electrical signals generated by soil could be used to indicate soil heavy metal pollution. .In this study, different types of soil would be collected as research subjects. Soil was packed into MFCs to generate power. We intended to illustrate the character of electrical signals with different soil types, and the soil physicochemical properties driving the electrical signals. We would uncover the sensitivity and linear range of electrical signals by soil in their response to typical heavy metal pollutants Zn, Cd and Pb. We would demonstrate the bacterial community and the community of active bacteria by using high throughput DNA sequencing and stable isotope probing technology, and demonstrate the influence of heavy metal pollution on these bacterial communities. We intended to isolate, culture and identify bacterial strains that contributed to power generation in soil contaminated with heavy metals. The stains include the electrogenic bacteria on anode and the cathodic bacteria which catalyze the electron transportation. We also attempted to illustrate the relationship between electrochemical properties and the concentrations of heavy metal pollutants. The research program would provide a theoretical reference for the development of a novel technology in monitoring soil pollution, and would expand the soil source bacterial strains that contributed to power generation.

土壤含有产电细菌，能在微生物燃料电池(MFCs)中产电。土壤产电电压或电流可作为土壤产电信号指示土壤重金属污染，污染程度越高，土壤产电信号越弱。指示过程优点在于实时连续和不耗能无污染。但尚不清楚土壤产电信号指示重金属污染的微生物机制。.本研究选择不同类型土壤作为研究对象。将土壤置于MFCs中产电，阐明不同类型土壤产电信号特征及影响产电的土壤理化性质因素；揭示不同土壤产电信号响应重金属污染物Zn、Cd、Pb的灵敏性和线性范围。采用高通量测序及稳定同位素探针技术揭示MFCs阳极和阴极表面细菌群落和“活跃的”细菌群落，以及重金属污染物对这些细菌群落的影响。分离培养重金属污染土壤中参与产电的细菌菌株并完成菌种鉴定，包括阳极产电细菌和阴极催化电子传递的细菌。揭示菌株的电化学性质与重金属污染物浓度之间关系。本项目意义在于为发展土壤污染监测新技术提供可靠理论依据，扩展土壤源的参与产电的微生物资源。

【项目背景】针对重金属污染事件的应急监测是目前急需的监测技术。应急监测要求对突发污染事件快速监测，从而迅速消除污染物的危害。但是传统监测方法依赖人工定期或不定期的采样或依靠群众举报，无法做到原位在线监测，对污染事件发现滞后，难以及时处理污染。另外，采样过程耗时费力、成本较高。因此，探索原位在线监测土壤或湿地重金属污染事件的技术对于实现应急监测，维护环境安全具有重要意义。我们发现土壤中普遍含有大量产电细菌，它们的产电电压对环境变化响应敏感，可用于发展原位在线监测新技术。.【主要研究内容】1）土壤产电信号及产电细菌研究；2）基于土壤产电信号传感器监测重金属污染研究；3）土壤产电信号响应重金属污染的电化学和微生物学机制。.【重要结果和关键数据】1）我们首先提出“产电细菌相关属”的概念，较好的克服了土壤产电细菌因缺乏通用引物而无法表征多样性的问题，从而揭示了全国范围三十七个土壤样本的土壤产电细菌数量、组成和多样性。结果表明，旱地和湿地土壤中产电细菌数量分别约占总细菌数量的1%和2%，分布于16个产电细菌相关属。并分离鉴定了土壤源的产电细菌新种生孢梭菌(Clostridium sporogenes)；2）发明了利用土壤产电细菌产电信号原位在线监测湿地重金属污染的传感器，该传感器电信号可以响应连续多次重金属污染，并在野外环境下连续工作八个月；3）揭示了该传感器响应重金属污染的电化学和微生物学机制。重金属溶液含有的大量氢离子以及二价铜或六价铬离子可在阴极还原，消耗阴极表面大量电子，引起阴极电势和传感器电压升高。而约有99%的重金属离子进入土壤后被吸附固定，无法对土壤产电细菌活性造成抑制。.【科学意义】1）为发展原位在线监测土壤和湿地重金属污染事件的应急监测新技术提供可靠的理论和实践依据；2）揭示土壤产电细菌数量和多样性并扩展产电细菌资源库，为深入研究土壤产电细菌提供了数据和方法借鉴。

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