Berger S, Shaw D R, Berben T, Ouboter H T, In 't Zandt M H, Frank J, Reimann J, Jetten M S M, Welte C U
Institute for Water and Wetland Research, Department of Microbiology, Radboud University, Nijmegen, the Netherlands.
Biological and Environmental Science and Engineering Division, Water Desalination and Reuse Research Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia.
Biofilm. 2021 Jun 15;3:100054. doi: 10.1016/j.bioflm.2021.100054. eCollection 2021 Dec.
In recent years, the externalization of electrons as part of respiratory metabolic processes has been discovered in many different bacteria and some archaea. Microbial extracellular electron transfer (EET) plays an important role in many anoxic natural or engineered ecosystems. In this study, an anaerobic methane-converting microbial community was investigated with regard to its potential to perform EET. At this point, it is not well-known if or how EET confers a competitive advantage to certain species in methane-converting communities. EET was investigated in a two-chamber electrochemical system, sparged with methane and with an applied potential of +400 mV versus standard hydrogen electrode. A biofilm developed on the working electrode and stable low-density current was produced, confirming that EET indeed did occur. The appearance and presence of redox centers at -140 to -160 mV and at -230 mV in the biofilm was confirmed by cyclic voltammetry scans. Metagenomic analysis and fluorescence hybridization of the biofilm showed that the anaerobic methanotroph ' Methanoperedens BLZ2' was a significant member of the biofilm community, but its relative abundance did not increase compared to the inoculum. On the contrary, the relative abundance of other members of the microbial community significantly increased (up to 720-fold, 7.2% of mapped reads), placing these microorganisms among the dominant species in the bioanode community. This group included sp., sp., two members of the Bacteroidetes phylum, and the spirochete sp. Genes encoding proteins putatively involved in EET were identified in sp., sp. and one member of the Bacteroidetes phylum. We suggest that instead of methane, alternative carbon sources such as acetate were the substrate for EET. Hence, EET in a methane-driven chemolithoautotrophic microbial community seems a complex process in which interactions within the microbial community are driving extracellular electron transfer to the electrode.
近年来，在许多不同的细菌和一些古菌中发现了电子作为呼吸代谢过程一部分的外化现象。微生物细胞外电子转移（EET）在许多缺氧的自然或工程生态系统中发挥着重要作用。在本研究中，对一个厌氧甲烷转化微生物群落进行了研究，以探讨其进行EET的潜力。目前，尚不清楚EET是否以及如何赋予甲烷转化群落中某些物种竞争优势。在一个两室电化学系统中对EET进行了研究，该系统通入甲烷，相对于标准氢电极施加 +400 mV的电位。工作电极上形成了生物膜，并产生了稳定的低密度电流，证实EET确实发生了。通过循环伏安扫描证实了生物膜中 -140至 -160 mV和 -230 mV处氧化还原中心的出现和存在。对生物膜的宏基因组分析和荧光杂交表明，厌氧甲烷氧化菌“Methanoperedens BLZ2”是生物膜群落的重要成员，但其相对丰度与接种物相比并未增加。相反，微生物群落其他成员的相对丰度显著增加（高达720倍，占映射读数的7.2%），使这些微生物成为生物阳极群落中的优势物种。该群体包括sp.、sp.、拟杆菌门的两个成员以及螺旋体sp.。在sp.、sp.和拟杆菌门的一个成员中鉴定出了推测参与EET的蛋白质编码基因。我们认为，替代碳源如乙酸盐而非甲烷是EET的底物。因此，在甲烷驱动的化能自养微生物群落中，EET似乎是一个复杂的过程，其中微生物群落内部的相互作用驱动着细胞外电子向电极的转移。
