微生物纳米导线的导电机制及功能

Electrical conductivity and application of microbial nanowires

微生物胞外呼吸是厌氧环境中控制性能量代谢方式,直接驱动着C、N、S、Fe等关键元素的生物地球化学循环。微生物纳米导线(Microbial nanowires)的发现,被认为是微生物胞外呼吸的里程碑事件,推动了电微生物学(Electromicrobiology)的形成与发展。微生物纳米导线是一类由微生物合成的,具有导电性的纤维状表面附属结构。通过细菌纳米导线,微生物胞内代谢产生的电子可以长距离输送到胞外受体或其他微生物,改变了电子传递链仅仅局限于细胞胞内的认识,从而大大拓展了微生物-胞外环境互作的范围。微生物纳米导线的良好导电性,赋予了其作为天然纳米材料的广阔应用前景。目前,微生物纳米导线的导电机制、生态功能及其在生物材料、生物能源、生物修复及人体健康多领域的应用,已经成为新兴电微生物学的前沿与热点。然而,微生物纳米导线的生物学、生态学功能尚不清楚,它的电子传递机制仍存在分歧。本文在系统性总结微生物纳米导线性质、功能的基础上,以Geobacter sulfurreducens和Shewanella oneidensis纳米导线为模型,详细阐述了纳米导线的组成与结构、表征与测量方法、导电理论(类金属导电学说与电子跃迁学说)及其潜在的应用,最后提出了未来微生物纳米导线研究的重点方向、挑战与机遇。

The extracellular respiration of microbes is the key energy metabolism in the anaerobic environment,driving the global biogeochemical cycle of some key elements,like C,N,S and Fe.The discovery of microbial nanowire is a milestone in the study of extracellular respiration,which promoted the study of electromicrobiology.Microbial nanowires are conductive filaments growing on the surface of bacteria.They transfer intracellular metabolic electrons outward for the reduction of extracellular electron acceptors promoting extracellular respiration or they transfer electrons to other microbes forming syntrophic cocultures.This process broadens the knowledge on electron transfer in organism and expands the interactions between microorganism and the natural environment.Owing to the excellent conductivity,microbial nanowires have the prospect of a broad application.Studies on the conductivity,ecological functions and the applications in biomaterials,bioenergy,bioremediation and human health of microbial nanowires have been regarded as a pioneering field and the focus of research in electromicrobiology.However,the biological and ecological functions of microbial nanowires are unknown and the mechanism of electron transfer along nanowire is ambiguous.Here,we will begin by summarizing all published microbial nanowires and their reported characteristics and functions.Two representatives of Geobacter sulfurreducnes and Shewanella oneidensis are included to introduce the composition and structure of their microbial nanowires.Furthermore,after presenting the methods and technologies used for conductivity measurement,the conductivity models of microbial nanowires(metabolic-like conductivity and electron hopping)are discussed and compared.We also suggest future studies and applications of microbial nanowires.The problems,challenges and opportunities analyses of microbial nanowire study are also provided.