It has been recently shown that magnetite nanoparticles (nanoFe₃O₄) can facilitate methanogenic syntrophy but the effect of magnetite on methanogenesis alone remains elusive. Here we show that aceticlastic methanogenesis by Methanosarcina mazei is accelerated by magnetite and is correlated with the redox cycling of structural Fe(II) and Fe(III) in the mineral. An enrichment and its closest pure culture relative, Ms. mazei zm‐15, both obtained from a natural wetland of the Tibetan plateau were tested in this experiment. The Fe(II) to Fe(III) ratios in magnetite, as measured by multiple approaches, show an initial increase in both the methanogenic cultures and the blank preparations containing no microbes. The Fe(II)/Fe(III) ratio then displays a distinct decline followed by an increase towards the end of incubation only in the enrichment and pure culture cultivations. This redox cycling of magnetite is in accordance with the stimulation of aceticlastic methanogenesis. Microscopic observation reveals the precipitation of nanoFe₃O₄ on methanogen cell surface. The genomic analysis predicts that in addition to electron transfer components essential for aceticlastic methanogenesis, Ms. mazei zm‐15 contains an outer‐surface multiheme c‐type cytochrome (MHC) and a few function‐unknown surface proteins that harbour monoheme motif. We hypothesize that the redox cycling of nanoFe₃O₄ delivers a positive influence via the MHC to the membrane electron transfer chain and hence promote the aceticlastic methanogenesis.

中文翻译：

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磁铁矿中Fe（II）和Fe（III）的氧化还原循环通过马氏甲烷八叠球菌加速了乙酸弹状甲烷化作用。

最近已经显示，磁铁矿纳米颗粒（nanoFe ₃ O ₄）可以促进产甲烷作用，但是仅凭磁铁矿对产甲烷作用的作用仍然难以捉摸。在这里，我们表明，磁铁矿加速了甲烷甲烷八叠球菌的破土性甲烷生成，并与矿物中结构Fe（II）和Fe（III）的氧化还原循环相关。女士及其亲属的纯净文化。马泽zm-15，都是从青藏高原的天然湿地获得的，在本实验中进行了测试。通过多种方法测得的磁铁矿中Fe（II）与Fe（III）的比率显示，产甲烷菌培养物和不含微生物的空白制剂均出现了初始增加。然后，Fe（II）/ Fe（III）的比值显示出明显的下降，然后仅在富集和纯培养条件下才开始温育。磁铁矿的这种氧化还原循环是根据对弹塑性产甲烷作用的刺激。显微镜观察揭示了纳米Fe ₃ O ₄在产甲烷菌细胞表面上的沉淀。基因组分析预测，除了对于乙破产甲烷菌必不可少的电子转移成分外，Ms。mazei zm-15包含外表面多血红素c型细胞色素（MHC）和一些带有单血红素基序的功能未知的表面蛋白。我们假设nanoFe ₃ O ₄的氧化还原循环通过MHC传递了积极的影响到膜电子转移链，因此促进了乙弹甲烷化作用。