Methanosarcina barkeri Raw sequence reads

Application of current can stimulate biomass removal and methane production in anaerobic digesters where Methanosarcina are frequently found. Therefore, the impact of current on methanogenesis by M. barkeri was examined. Cells were grown in reactors with methanol and cathodes poised at different potentials (-0.6 V and -1.0 V vs. Ag/AgCl). CH4/CO2 ratios (4.9:1 and 5.6:1) and CO2 conversion efficiencies (24% and 43%) for the -0.6V and -1.0V reactors were higher than the non-current control reactor (3.46:1 and 7%). Cathodic H2 provided an additional source of electrons in the -1.0V reactor, however, no electron mediators were detected in the -0.6V reactor. Cells were tightly attached to the -0.6V cathode, suggesting that M. barkeri obtained additional electrons directly from the -0.6V cathode. Transcriptomics revealed that genes for methylotrophic methanogenesis, CO2 reduction, carbon fixation, and intracellular hydrogen cycling were more highly expressed in current-exposed cells than the non-current control. In particular, transcripts for Vht and Frh hydrogenase genes were > 3.4 times more abundant in cells grown with poised cathodes. These results show that M. barkeri uses similar pathways for electron uptake in the presence of current, whether electrons are being acquired directly from the cathode surface or indirectly from cathodic H2.

施加电流可在常检出甲烷八叠球菌属（Methanosarcina）的厌氧消化器中促进生物质去除与甲烷生成。因此本研究考察了电流对巴氏甲烷八叠球菌（Methanosarcina barkeri，简称M. barkeri）产甲烷过程的影响。实验采用以甲醇为底物的反应器，将阴极电位分别控制为-0.6 V与-1.0 V（相对于Ag/AgCl参比电极）以培养菌体。-0.6 V与-1.0 V组反应器的甲烷/二氧化碳比值（分别为4.9:1与5.6:1）及二氧化碳转化效率（分别为24%与43%）均高于无电流对照组（3.46:1与7%）。在-1.0 V组反应器中，阴极产生的氢气为菌体提供了额外的电子供体；而-0.6 V组反应器中未检测到电子介导物。菌体紧密附着于-0.6 V组的阴极表面，这表明巴氏甲烷八叠球菌可直接从阴极获取额外电子。转录组学（Transcriptomics）分析显示，与无电流对照组相比，经电流处理的菌体中，甲基营养型产甲烷、二氧化碳还原、碳固定及胞内氢循环相关基因的表达水平显著上调。尤为值得注意的是，在阴极电位受控的培养条件下，菌体中Vht与Frh氢化酶基因的转录本丰度较对照组高出3.4倍以上。上述结果表明，无论直接从阴极表面获取电子，还是间接通过阴极产生的氢气获取电子，巴氏甲烷八叠球菌均采用相似的电子摄取代谢途径。