Extracellular electron transfer through microbial reduction of solid-phase humic substances
Extracellular electron transfer through microbial reduction of solid-phase humic substances
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DOI：
10.1038/ngeo870
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发表时间：
2010-06-01
影响因子：
18.3
通讯作者：
Xu, Huifang
中科院分区：
文献类型：
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作者：
Roden, Eric E.;Kappler, Andreas;Xu, Huifang
土壤和沉积有机质的腐烂产生高分子量的有机化合物，称为腐殖质(1)。微生物可以将电子传递给溶解的腐殖质物质(2)，还原的腐殖质物质可以快速还原铁（III）氧化物(3)。因此，溶解的腐殖质物质可以作为促进沉积物中铁（III）氧化物还原的电子穿梭体（2,4）。然而，土壤和沉积物中的大多数腐殖质都是颗粒状的，而不是溶解的(1)；微生物减少固相腐殖质的能力及其传送电子的能力迄今尚不清楚。在这里，我们通过培养实验和电子自旋共振测量表明，铁（III）氧化物还原细菌可以将电子转移到从湿地取样的沉积物中的固相腐殖质中。虽然固相腐殖质的电子接受能力不大，但固相腐殖质通过将电子从细菌传送到氧化物表面，显著加速了铁（III）氧化物的还原。微生物固相腐殖质还原是一种新的细胞外电子转移机制，可以促进沉积物和土壤中氧化铁（III）的还原和其他氧化还原反应。
The decay of soil and sedimentary organic matter yields organic compounds with a high molecular weight, termed humic substances(1). Microorganisms can transfer electrons to dissolved humic substances(2), and reduced humic substances can rapidly reduce iron(III) oxides(3). Thus, dissolved humic substances can serve as electron shuttles that promote iron( III) oxide reduction in sediments(2,4). However, most humic substances in soils and sediments are in particulate, rather than dissolved, form(1); the ability of microorganisms to reduce solid-phase humics and their capacity to shuttle electrons is thus far unknown. Here we show through incubation experiments and electron spin resonance measurements that iron(III)-oxide-reducing bacteria can transfer electrons to solid-phase humic substances in sediments sampled from wetlands. Although the electron-accepting capacity of the solid-phase humics was modest, solid-phase humics significantly accelerated iron(III) oxide reduction, by shuttling electrons from bacteria to oxide surfaces. Microbial solid-phase humics reduction represents a new mechanism for extracellular electron transfer that can facilitate reduction of iron(III) oxide and other redox reactions in sediments and soils.