磁铁矿促进微生物种间电子传递的机制

Mechanisms of interspecific electron transfer promoted by magnetite

磁铁矿是自然界中广泛存在的矿物之一,其与互营微生物间的直接接触过程中常常伴随发生不同的电子传递“策略机制”,从而直接或间接地提升了微生物的种间电子传递(interspecific electron transfer,IET)过程,有助于互营微生物间的共生长及代谢.这种效应将促进一些环境新能源的可再生应用.系统综述了基于磁铁矿促进强化IET过程中的主要作用机制:(1)磁铁矿具有良好的氧化还原特性,可作为储存电子的“环境电池”;(2)磁铁矿表现出良好的导电性,可与OmcS蛋白具有等同效应;(3)磁铁矿对微生物具有特定的生理应激效应,可刺激胞外聚合物的分泌并激活与电子相关的酶活性等.概述了现阶段磁铁矿作为一种廉价的介导材料用于提升IET的环境应用,特别是在强化生物甲烷应用实现二氧化碳减排、微生物脱氯、脱氮及厌氧氧化甲烷等生物工程应用领域中具有无限潜力.针对现阶段应用磁铁矿提升IET环境过程中存在的不足,提出:(1)将磁铁矿作填充床,作为内置厌氧消化装置;(2)对磁铁矿进行修饰/改性,降低铁流失从而提高其稳定性.未来工作将聚焦在结合多组学、同位素标记及搭建可行的方法体系,解析磁铁矿强化直接IET(DIET)作用机制,并深入探究磁铁矿的铁磁效应及促进DIET过程的关联效应.

Magnetite is a mineral that is abundant in nature. In the coexistence of magnetite with syntrophic microorganisms, differential strategies for transferring electrons are mediated by magnetite, which may directly or indirectly influence the interspecific electron transfer(IET) process. This would be beneficial for the cogrowth and metabolism of syntrophic microorganisms. Notably, this promotional effect will improve several environmental applications of renewable energy. In this study, several mechanisms regarding the magnetitepromoting IET process are systematically elaborated. The main mechanisms are:(1) magnetite possesses favorable redox properties that could serve as “environmental batteries”,(2) magnetite displays electrical conductivity equivalent to that of OmcS proteins, and(3) magnetite induces certain physiological responses in microorganisms by stimulating the secretion of extracellular polymeric substances and hopping the activities of enzymes related to electron transfer stimulated by magnetite. Environmental applications regarding the enhancement of IET with magnetite as a low-cost mediated material are currently increasing, especially the promotion of methanogenesis by fixing carbon dioxide, microbial dechlorination and denitrification, and anaerobic oxidation of methane. Finally, to address the shortcomings in the application of magnetite to promote IET, two improvement solutions are proposed. To improve the stability of magnetite, it could be filled in an inbuilt packed bed of an anaerobic-digestion reactor and modified to reduce the loss of iron. Moreover, more research should focus on employing multi-omics and isotope labeling technology and establishing a feasible system to elaborate the mechanism of the enhanced direct IET(DIET) process. Furthermore, the correlation between the ferromagnetic effect of magnetite and enhanced DIET should also be explored in depth.