| Resource & environmental sciences |
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| Progress in research of electron transfer mediator (ETM) |
| DING Aqiang, ZHENG Ping*, ZHANG Meng |
| College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China |
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Abstract Electron transport chain (ETC) consists of a series of compounds which is arranged according to electron affinity to transport electron. Respiratory process is the main source of energy in microbe, however, with many blind spots for restriction of insitu research. It is generally acknowledged that, ETC possesses close relationship with respiratory process, which provides a possible way to further research of ETC and respiratory in microbe.
In general, electron is considered to transfer from extracellular into intracellular through respiratory chain. However, recent studies have demonstrated that electron can also transfer through inverse way, i.e. from intracellular to extracellular. Three main mechanisms were hypothesized for electron transfer: 1) through direct contact, 2) through nanowire, 3) utilizing electron transfer mediator (ETM). Among these researches, the ETM should be paid more attention, for which plays key roles in intracellular physiological as well as in extracellular ecological processes. It is reported that ETMs usually take part in many redox reactions in intracellular and act as a link between these reactions in the respiratory chain. Besides, they can also take electrons to the inside or outside of the cell, expanding cell’s metabolic domain.
ETM can be classified into cellular synthesized (physiological ETM, PETM) and extracellular synthesized (nonphysiological ETM, nPETM) by the source. PETMs include many small molecules, such as phenazine and flavin. Phenazine is a kind of nitrogenous heterocyclic compound, and four main phenazine, i.e. phenazine1carboxylate, pyocyanin, phenazine1carboxamide and 1hydroxyphenazine are common in microbe. Their redox potentials are between -40 to -174 mV, indicating NADH or coenzyme Q is the ideal position for the electron transfer from electron donor. Flavin is a kind of isoalloxazine derivative, and three main compounds are riboflavin, flavin adenine dinucleotide and flavin mononucleotide. They have similar redox potential to phenazine as well as the electron transfer pathway. nPETMs mainly include humus and AQDS. Both of them have benzoquinonyl, indicating that they can transfer electron through variation between benzoquinonyl and phenolic group. Besides, some humus, such as dimethyl sulfone and Nmethylaniline, can transfer electron by nitrogen or sulfur containing group.
The utilization of PETM and nPETM has raised more and more attention in environmental pollution control, for their effects in microorganism biodegradation. Recent research focused on microbial fuel cell and microbial electrolysis cell, has proved that the additions of PETM and nPETM can enhance contaminant removal in the control of dye, uranium and other metals pollution. Further research had demonstrated that the additional PETM and nPETM showed positive correlation with pollutant removal.
Clarifying the physiological and ecological functions of ETM would benefit the comprehensive of microbial electrochemical process and the development of bioremediation technology, as well as the development of microbial fuel cell (MFC) and microbial electrolysis cell (MEC). In this paper, a review on the chemical construction, redox potential, electron transfer mechanism and application in environmental biotechnology of typical ETMs was presented.
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Published: 20 September 2016
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电子介体研究进展
电子介体不仅在胞内生理过程中起着核心作用,也在胞外生态过程中起着重要作用。探明电子介体的生理生态功能,对于微生物电化学过程的研究和污染生物修复技术的研发具有重大的现实意义。电子介体可分为细胞合成的生理性电子介体和非细胞合成的非生理性电子介体。本文综述了几种典型的生理性电子介体和非生理性电子介体的化学结构、氧化还原电位、电子传递机制及其在环境生物技术研发中的应用。
关键词：
电子传递链,
生理性电子介体,
非生理性电子介体,
生理生态意义
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