Molecular Microbial Ecology Group, Institute of Aquatic Ecology, University of Girona, Girona, Spain.
LEQUiA, Institute of the Environment, University of Girona, Girona, Spain.
PLoS One. 2019 Apr 11;14(4):e0215029. doi: 10.1371/journal.pone.0215029. eCollection 2019.
Electromethanogenesis is the bioreduction of carbon dioxide (CO2) to methane (CH4) utilizing an electrode as electron donor. Some studies have reported the active participation of Methanobacterium sp. in electron capturing, although no conclusive results are available. In this study, we aimed at determining short-time changes in the expression levels of [NiFe]-hydrogenases (Eha, Ehb and Mvh), heterodisulfide reductase (Hdr), coenzyme F420-reducing [NiFe]-hydrogenase (Frh), and hydrogenase maturation protein (HypD), according to the electron flow in independently connected carbon cloth cathodes poised at- 800 mV vs. standard hydrogen electrode (SHE). Amplicon massive sequencing of cathode biofilm confirmed the presence of an enriched Methanobacterium sp. population (>70% of sequence reads), which remained in an active state (78% of cDNA reads), tagging this archaeon as the main methane producer in the system. Quantitative RT-PCR determinations of ehaB, ehbL, mvhA, hdrA, frhA, and hypD genes resulted in only slight (up to 1.5 fold) changes for four out of six genes analyzed when cells were exposed to open (disconnected) or closed (connected) electric circuit events. The presented results suggested that suspected mechanisms for electron capturing were not regulated at the transcriptional level in Methanobacterium sp. for short time exposures of the cells to connected-disconnected circuits. Additional tests are needed in order to confirm proteins that participate in electron capturing in Methanobacterium sp.
电甲烷生成是利用电极作为电子供体将二氧化碳（CO2）还原为甲烷（CH4）的生物还原过程。一些研究报道了 Methanobacterium sp. 在电子捕获中的积极参与，尽管没有确凿的结果。在这项研究中，我们旨在根据独立连接的碳纤维阴极中的电子流，确定 [NiFe]-氢化酶（Eha、Ehb 和 Mvh）、异二硫化物还原酶（Hdr）、辅酶 F420 还原 [NiFe]-氢化酶（Frh）和氢化酶成熟蛋白（HypD）的表达水平在短时间内的变化，这些阴极在相对于标准氢电极（SHE）的-800 mV 下处于平衡状态。阴极生物膜的扩增子大规模测序证实了富集的 Methanobacterium sp. 种群的存在（>70%的序列读数），该种群仍处于活跃状态（78%的 cDNA 读数），将这种古菌标记为该系统中主要的甲烷产生菌。当细胞暴露于开路（断开）或闭路（连接）电路事件时，对六个分析基因中的四个基因（ehaB、ehbL、mvhA、hdrA、frhA 和 hypD）的定量 RT-PCR 测定结果仅略有变化（高达 1.5 倍）。研究结果表明，在 Methanobacterium sp. 细胞短时间暴露于连接-断开电路时，电子捕获的可疑机制并未在转录水平上受到调节。需要进行额外的测试以确认参与 Methanobacterium sp. 电子捕获的蛋白质。
