This study was conducted to delineate microbial community development and composition on both working and counter electrodes in single-chamber microbial electrolysis cells (MECs) using synthetic wastewater. Two separate bioelectrochemical reactors were inoculated with anaerobic sludge. The first was operated at an anodic potential poised at + 0.4 V and the second one at a cathodic potential poised at -0.7 V, both vs. an Ag/AgCl reference electrode. The performance of the MECs, including current generation, bioelectrochemical activity of the biofilms on both the working and counter electrodes, and chemical oxygen demand (COD) depletion were monitored over the last 45 days of operation. Scanning electron microscopy (SEM) and 16S rRNA gene sequencing were performed to delineate the development and morphology of the microbial communities on both the working and the counter electrodes. The current generated at the anodic working electrode provided evidence of the growth of anode-respiring exoelectrogens (Clostridium sensu stricto). Similarly, the Faradaic current data at the cathodic working electrode confirmed the formation of an electroactive biofilm dominated by acetoclastic and hydrogenotrophic methanogens (Methanothrix and Methanobacterium). Microbial communities on the counter electrodes were found to be richer but less diverse compared to those on the working electrodes. These communities were likely influenced by the fluctuating potentials at the counter electrodes. SEM observations were consistent with the microbial analysis. These findings demonstrate the ability of a mixed inoculum to shift towards anode-reducing and cathode methanogenic communities using a complex substrate on a constant working electrode and varying counter electrode potentials.

Keywords: Anodic biofilms; Cathodic biofilms; High-throughput sequencing; Microbial community; Microbial electrolysis cells.

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本研究旨在通过使用合成废水在单室微生物电解池（MECs）中描述工作电极和计数电极上微生物群落的发展和组成。两个独立的生物电化学反应器被用厌氧污泥接种。第一个反应器的操作电位为+0.4 V，第二个反应器操作电位为-0.7 V，均相对于Ag/AgCl参比电极而言。在最后45天运行期间，监测了MECs的性能，包括电流产生、工作和计数电极上生物膜的生物电化学活性以及化学需氧量（COD）的减少。通过扫描电子显微镜（SEM）和16S rRNA基因测序来描述工作电极和计数电极上微生物群落的发展和形态。在阳极工作电极产生的电流提供了厌氧产电菌（Clostridium sensu stricto）生长的证据。同样，阴极工作电极处法拉第电流数据证实了由乙酸盐型和氢型甲烷生成菌（Methanothrix 和 Methanobacterium）主导的电活性生物膜形成的形成。发现计数电极上的微生物群落比工作电极上的更丰富但多样性更低，这些群落可能是由于计数电极上波动电位的影响所致。SEM观察结果与微生物分析一致。这些研究结果表明，在使用复杂基质和恒定的工作电极以及变化的计数电极电位的情况下，混合接种物能够向阳极还原和阴极甲烷化社区转变的能力。

关键词：阳极生物膜；阴极生物膜；高通量测序；微生物群落；微生物电解池。