Collaborative Research: Mechanisms, Modeling and Geochemical Consequences of Electron Flow in Acid Mine Drainage-Induced Sediments

合作研究：酸性矿山排水诱发沉积物中电子流的机制、模拟和地球化学后果

• 批准号: 1148498
• 负责人: Yuri Gorby
• 金额: $ 25.32万
• 依托单位: University of Southern California
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-15 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1148498&HistoricalAwards=false
• 关键词: Collaborative; Research; Mechanisms; Modeling; Geochemical

The transfer of material and energetic substrates for microbial metabolism has historically been viewed as strongly dependent on the diffusion of chemical species within the physicochemical milieu in which the microbial community is active. Ideas that individual organisms and microbial communities may mediate redox reactions despite spatial separation of energetic substrates have now begun to challenge this view. Microbial communities that are electrically integrated in a network of conductive extracellular structures (e.g. microbial nanowires) and redox-active mineral phases may facilitate and exploit the movement of electrons over scales (mm- to cm-scale) far exceeding those of the individual cells (micrometer to meter-scale), referred to as "far-afield extracellular electron transport (EET)." An important implication of farafield EET is that biogeochemical redox reactions may occur despite the spatial separation of reductant, oxidant, and even individual microorganisms themselves. The work proposed here will use an acid mine drainage (AMD)-impacted system to examine the dynamics of electron flow in a "natural" setting. In several settings, when Fe(II)-rich AMD reaches the terrestrial surface aerobic, acidophilic bacteria oxidize Fe(II) to Fe(III). The Fe(III) (hydr)oxides that result from these microbial activities accumulate as 'iron mounds,' which are composed almost exclusively of Fe(III) phases. It is hypothesized that integrated, conductive networks composed of mineral phases, microbial nanowires, and other conductive cellular material facilitate EET and the transfer of electrons through the iron mound, supporting microbiological oxidation of Fe(II) at depths within the iron mound that could not be sustained simply by diffusion of O2 into the mound. Field-based fine-scale geochemical site characterizations coupled with measurements of geo- and electro-chemical changes and detailed characterizations of electrically conductive microbial structures in laboratory-scale sediment incubations will be used to elucidate the rates, scales, and extents of electron transfer processes mediated by iron mound-associated microbial communities. Multiscale physical modeling of electron transfer processes will be used to support and supplement experimental examinations of electron transfer within this system, and will include modeling of electron flow in simulated microbial nanowires, 'biogeobatteries,' and in larger scale systems like that encountered in an iron mound. Results of this work will enhance understanding of microbially mediated geochemical processes in iron mounds and AMD treatment approaches. A non-profit AMD treatment company will serve as an unfunded collaborator on this project to facilitate knowledge transfer to AMD treatment practitioners. Funds from this project will aid in the interdisciplinary training of a post-doctoral researcher, graduate, and undergraduate students, while facilitating a strong collaboration between a public university (The University of Akron) and private university (The University of Southern California). Graduate and undergraduate students will be recruited from UA's McNair Scholars program. The iron mound field site will also serve as a field classroom for formal courses at UA and a local school district.

从历史上看，微生物代谢的材料和能量底物的转移非常依赖于微生物群落活跃的物理化学环境中化学物种的扩散。尽管有能量的底物的空间分离，但单个生物体和微生物群落可能会介导氧化还原反应的想法已经开始挑战这种观点。在电导细胞外结构网络（例如微生物纳米线）和氧化还原活性矿物相中有电的微生物群落可能会促进和利用电子超越尺度（MM-至CM尺度）的移动（远远超过单个细胞的尺度）（千分尺至仪表），称为“远场外电子传输（EET）”。法拉菲尔德EET的一个重要含义是，尽管还原剂，氧化剂甚至单个微生物本身，生物地球化学氧化还原反应可能会发生。这里提出的工作将使用酸性矿山引流（AMD）冲击系统来检查“自然”环境中电子流动的动力学。在几种情况下，当Fe（II）-Rich AMD到达陆地表面有氧，嗜酸细菌氧化为Fe（II）至Fe（iii）。这些微生物活性导致的Fe（III）（III）（Hyd）氧化物积聚为“铁丘”，几乎完全由Fe（III）阶段组成。假设由矿物相，微生物纳米线和其他导电细胞材料组成的集成，导电网络促进EET和电子通过铁丘的转移，从仅通过将O2扩散到土丘中来维持。基于现场的高尺度地球化学位点的特征，结合测量的地理和电化学变化以及实验室尺度沉积物孵化中电导导电微生物结构的详细表征将用于阐明电子传递过程的速率，范围和扩展。由铁丘相关的微生物群落介导。 电子传输过程的多尺理建模将用于支持和补充该系统中电子传递的实验检查，并包括模拟的微生物纳米线中电子流的建模，“生物地焦点”，以及在类似的较大规模系统中，在类似的较大规模系统中冢。这项工作的结果将增强对铁丘和AMD处理方法中微生物介导的地球化学过程的理解。一家非营利性AMD治疗公司将担任该项目的无资金合作者，以促进知识转移给AMD治疗从业人员。该项目的资金将有助于对博士后研究员，研究生和本科生进行跨学科培训，同时促进公立大学（阿克伦大学）和私立大学（南加州大学）之间的强有力合作。将从UA的McNair学者计划中招募研究生和本科生。 Iron Mound Field网站还将作为UA和当地学区正式课程的实地教室。