物理化学学报 >> 2019, Vol. 35 >> Issue (1): 22-27.doi: 10.3866/PKU.WHXB201801085

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扫描电化学显微镜用于研究生物膜微环境的电子传递

田晓春1,2,吴雪娥1,*(),詹东平1,赵峰2,姜艳霞1,*(),孙世刚1   

  1. 1 厦门大学化学化工学院,福建 厦门 361005
    2 中国科学院城市环境研究所,中国科学院城市污染物转化重点实验室,福建 厦门 361021
  • 收稿日期:2017-12-12 发布日期:2018-06-13
  • 通讯作者: 吴雪娥,姜艳霞 E-mail:xewu@xmu.edu.cn;yxijiang@xmu.edu.cn
  • 基金资助:
    国家重点研发计划项目(2017YFA0206500);国家自然科学基金(21777155);国家自然科学基金(21773198);国家自然科学基金(U1705253);国家自然科学基金(21621091)

Research on Electron Transfer in the Microenvironment of the Biofilm by Scanning Electrochemical Microscopy

Xiaochun TIAN1,2,Xuee WU1,*(),Dongping ZHAN1,Feng ZHAO2,Yanxia JIANG1,*(),Shigang SUN1   

  1. 1 College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian Province, P. R. China
    2 CAS Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, Fujian Province, P. R. China
  • Received:2017-12-12 Published:2018-06-13
  • Contact: Xuee WU,Yanxia JIANG E-mail:xewu@xmu.edu.cn;yxijiang@xmu.edu.cn
  • Supported by:
    the National Key Research and Development Program of China(2017YFA0206500);the National Natural Science Foundation of China(21777155);the National Natural Science Foundation of China(21773198);the National Natural Science Foundation of China(U1705253);the National Natural Science Foundation of China(21621091)

摘要:

生物电化学系统(BESs)的核心是生物膜在电极/溶液界面的电子传递反应,研究生物膜微区环境中的电子传递有助于阐明微生物的胞外电子传递(EET)机制,从而有针对性地提高BESs中的电子转移效率。微生物的EET机制包括直接电子传递和间接电子传递,由于生物膜组成复杂,含有多种分泌物、胞外聚合物等,常规电化学方法只能从生物膜宏观层面研究EET机制,无法有效区分这两种电子传递途径的贡献。本文采用电化学循环伏安方法研究了电子穿梭体二茂铁甲醇(FcMeOH)与希瓦氏菌(Shewanella)相互作用的界面过程;基于扫描电化学显微技术构建了穿透模式,通过微电极介导FcMeOH与Shewanella反应,收集仅来自间接电子传递途径产生的电流,同时测定了Shewanella在电极/溶液界面的氧化还原性质和空间分布。本论文将电化学扫描探针显微技术应用于EET的研究,从物理化学角度揭示微生物在代谢过程中与外界的电子传输机制。

关键词: 胞外电子传递, 希瓦氏菌, 扫描电化学显微镜, 穿透模式, 电子穿梭体

Abstract:

Microorganisms exploit extracellular electron transfer (EET) with external minerals during their growth. This process is accompanied by the conversion of chemical energy. Direct electron transfer (DET) from the microorganisms to solid electron acceptors via membrane-bound cytochrome c enzymes or conductive nanowires/pili has been reported. In previous studies, mediated electron transfer (MET) has also been demonstrated to occur through electrochemically active metabolites acting as redox mediators. The microorganisms with EET capabilities have been harnessed for bioelectrochemical systems (BESs) in the bioremediation of environmental contaminants and the production of biofuels and nanomaterials. Electron transfer at the electrode biofilm/solution interface is one of the core phenomena occurring in BESs. The study of the redox reactions occurring in the microenvironment of the biofilm should elucidate the mechanism of microbial EET, which will then help improve the electron transfer efficiency of BESs. The composition of a biofilm is complex and contains many redox secreta and extracellular polymeric substances. Therefore, the specific current generated from the DET or MET pathways cannot be solely detected using classic electrochemical methods. In the present study, the interfacial electron transfer of Shewanella oneidensis MR-1 on an ITO surface was investigated. Cyclic voltammetry (CV) was first applied to study the redox properties of Shewanella and its interaction with ferrocenylmethanol (FcMeOH), which served as an exogenous electron mediator. The cyclic voltammograms showed that the oxidation current of S. oneidensis MR-1 was dramatically enhanced in the presence of 0.01 mmol·L-1 FcMeOH compared to a control, i.e. bacterium-free ITO. This can be explained by the ability of S. oneidensis MR-1 to reduce FcMeOH+ during the positive scan. These results also showed that FcMeOH was a good redox mediator and capable of transferring electrons between the electrode and the bacterial cells. In addition, using the penetration mode in scanning electrochemical microscopy, the current generated from the MET by FcMeOH was collected using a microelectrode. Examination of the approaching curve showed that the current started to increase when the tip was approaching the solution/biofilm interface, providing positive feedback for the FcMeOH-mediated electron transfer between the microelectrode and the bacterial cells. The electrode biofilm/solution microenvironment was also detected, showing the thickness of the solution/biofilm to be 500 μm and the thickness of the biofilm to be 1100 μm. This study indicates that scanning electrochemical microscopy can be used in studying microbial MET. It also provides insight into the electron transfer mechanism of the microbial metabolism from a physical chemistry perspective.

Key words: Extracellular electron transfer, Shewanella, Scanning electrochemical microscopy, Penetration mode, Electron shuttle

MSC2000: 

  • O646