The biomineralization of metals by microorganisms in organic sediments

微生物驱动着控制矿物中所含金属流动性的关键过程，这些金属被吸附在有机和无机基质上，并溶解在地球表面的水中。我的研究项目集中在解释地球表面环境中常见的微生物如何通过呼吸控制电子转移反应来影响金属迁移；有些微生物可以利用金属作为电子供体和终端电子受体。由于呼吸作用，某些金属的氧化态会发生变化，从而极大地影响它们的溶解度。当这些过程产生富含金属的沉淀物时，就会产生生物矿物。目前尚不清楚金属的微生物呼吸如何促进寒冷的北方泥炭湿地的金属循环。这是一个适用于所有泥炭地的重要知识缺口，但我选择关注受采矿活动影响的地区，因为：1)目标元素浓度的升高为了解金属生物地球化学提供了独特的环境；2)湿地缓冲金属向水系释放的能力了解甚少；3)某些化学物质排放对生态系统健康具有破坏性。未来的气候变暖和更极端的水文制度波动可以通过改变微生物呼吸和影响生物矿物质的溶解度来影响微生物过程。本研究旨在了解a)微生物呼吸和氧暴露引起的氧化还原波动对加拿大北部某些矿山有机质、铁和重要靶元素（U、Cr）之间相互作用的影响；B)受微生物控制并与气候相关的影响泥炭基质中目标金属生物矿化的关键因素，以及c)本地泥炭湿地系统在气候波动期间缓冲金属通量的能力。实现这些目标需要以地球化学和微生物学为基础的跨学科方法。实现目标的项目包括：1)使用批处理系统，在微生物呼吸产生的还原和氧化条件循环中，氧化铁、有机物和U或Cr之间的动态关系；2)温度和水饱和度变化过程中，流动细胞对泥炭湿地基质中U、Cr和Fe的生物矿化作用；3)在U、Cr和Fe存在下，模拟气候波动时流动池系统微生物群落结构的变化；4)原生原地泥炭地在潮湿、寒冷条件下（春季）和温暖、干燥条件下（初秋）金属收支之间的联系；5)季节对原生泥炭地微生物群落的影响及特定微生物群与金属动态的相关性。该研究项目将为研究生和本科生提供重要的实验室和现场技术培训。学生将被训练使用多学科范围的方法，包括从分子到宏观的观察和分析尺度。开发新的实验方法，如x射线吸收光谱和分析金属化学技术，将提供重要的培训，并将有助于实现我的研究计划的目标。结果将是关于有机湿地中金属-微生物相互作用动力学的新基础知识。

Microorganisms drive key processes controlling the mobility of metals that are contained in minerals, adsorbed to organic and inorganic substrates, and dissolved in water at the Earth's surface. My research program centers on explaining how microbes common in Earth surface environments impact metal mobility by controlling electron transfer reactions through respiration; some microbes can use metals as electron donors and terminal electron acceptors. Changes to the oxidation state of some metals as a consequence of respiration can drastically impact their solubility. Biominerals result when such processes result in metal-rich precipitates. It is unknown how the microbial respiration of metals contributes to metal cycling in cold, northern peat wetlands. This is an important knowledge gap applicable to all peatlands, but I have chosen to focus on areas impacted by mining activities because: 1) the elevated concentrations of target elements provide a unique setting to understand metal biogeochemistry; 2) the capacity of wetlands to buffer metal releases to water systems is poorly understood; 3) the environmental impacts of some chemical discharges can be devastating to ecosystem health. Future climate warming and more extreme fluctuations in hydric regimes can be expected to affect microbial processes by altering microbial respiration, and by impacting the solubility of biominerals. This research is targeted at understanding a) the impacts of redox fluctuations induced by microbial respiration and oxygen exposure on the interactions between organic matter, iron and important target elements associated with some mines in northern Canada (U, Cr); b) the critical factors controlled by microbes and related to climate that impact biomineralization of target metals in peat substrates, and c) the capacity of native peat wetland systems to buffer metal fluxes during climate fluctuations.Addressing these objectives requires an interdisciplinary approach grounded in both geochemistry and microbiology. Projects to achieve the objectives include: 1) The dynamic relationship between iron oxide, organic matter, and U or Cr during cycles of reducing and oxidizing conditions created by microbial respiration, using batch systems; 2) Biomineralization of U, Cr, and Fe in a peat wetland substrate using flow cells, during changes in temperature and water saturation; 3) Changes in microbial community structure during simulated climate fluctuations in the flow cell system, in the presence of U, Cr and Fe; 4) The links between metal budgets in native, in situ peatlands during wet, cold conditions (spring) and warm, dry conditions (early fall); 5) Seasonal impacts on microbial communities and the correlation of specific microbial groups with metal dynamics in native peatlands.The research program will provide important training in laboratory and field techniques for graduate and undergraduate students. Students will be trained to use a multidisciplinary range of approaches that encompass observational and analytical scales that range from molecular to macroscopic. Developing novel experimental methods, such as X-ray absorption spectroscopy and analytical metal chemistry techniques, will provide important training, and will contribute critically to meeting the objectives of my research program. The outcome will be new fundamental knowledge on the dynamics of metal-microbe interactions in organic wetlands.