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流动性;一些微生物可以使用金属作为电子供体和终端电子受体。由于呼吸作用而导致的某些金属氧化态的变化会极大地影响其溶解度。当这种过程导致富含金属的沉淀物时，就会产生生物矿物。在寒冷的北方泥炭湿地中，微生物对金属的呼吸作用如何促进金属的循环尚不清楚。这是一个适用于所有泥炭地的重要知识差距，但我选择重点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）湿地缓冲金属释放到水系统的能力知之甚少; 3）一些化学品排放的环境影响可能对生态系统健康造成毁灭性的影响。未来的气候变暖和更极端的波动，在氢制度可以预期影响微生物的过程，通过改变微生物呼吸，并通过影响生物矿物的溶解度。本研究旨在了解a）由微生物呼吸和氧气暴露引起的氧化还原波动对有机质、铁和与加拿大北方某些矿山有关的重要目标元素（U、Cr）之间相互作用的影响; B）影响泥炭基质中目标金属生物成矿作用的关键因素，这些因素受微生物控制，与气候有关，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。为实现这一目标，开展的项目包括：1）利用间歇系统研究在微生物呼吸产生的还原和氧化条件下氧化铁、有机质和铀或铬之间的动态关系; 2）利用流动池研究在温度和水饱和度变化过程中泥炭湿地基质中铀、铬和铁的生物矿化; 3）在U、Cr和Fe存在下，在流动池系统中模拟气候波动期间微生物群落结构的变化; 4）在潮湿、寒冷的条件（春季）和温暖、干燥的条件下，天然原位泥炭地中金属收支之间的联系（初秋）; 5）对微生物群落的季节性影响以及特定微生物群体与原生泥炭地金属动力学的相关性。该研究计划将为研究生和本科生提供实验室和现场技术的重要培训。学生将接受培训，使用一系列多学科的方法，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。其结果将是新的基础知识的动态金属微生物在有机湿地的相互作用。

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.