Biogeochemical Cycling of Heavy Metals in Lake Coeur d'Alene Sediments: The Role of Indigenous Microbial Communities

重金属在环境中是剧毒的，它们在爱达荷州科达伦湖(LCdA)的沉积物中的存在主要是历史上上游山区采矿的结果。该项目的目标是：1)利用现代分子生物学技术表征沉积物中微生物的多样性；2)量化微生物群落中单个成员在金属(铜、铅和锌)生物地球化学循环中的作用；3)建立沉积物系统中重金属循环的动态数值生物地球化学模型，并根据LCDA的独特环境进行校准。这些目标将在检验以下总体假设的同时实现：在科达伦湖历史上被金属污染的沉积物中，存在着一个复杂和动态的微生物群落，这些微生物在系统发育上截然不同，以前没有特征。作为对有毒金属胁迫的响应，金属耐受性物种将主导存在于沉积物中的金属敏感物种，微生物的时空分布和多样性取决于金属类型和浓度。动态生物地球化学模型将化学传输和反应与新的微生物胁迫/响应关系和群落动力学结合在一起，可用于1)在空间和时间尺度上整合复杂的微生物和地球化学观测，以及2)更好地预测广泛的群落水平的响应和对有毒金属循环的影响。项目目标将通过采样LCdA沉积物和根据16S rDNA和rpoB基因序列确定微生物多样性来实现。这些分子技术极大地促进了对自然环境中微生物的研究，并将为观察社区对有毒金属添加的反应提供一个合理的平台。金属胁迫后微生物种群的变化将使用末端限制性片段长度多态性(T-RFLP)进行量化。重点实验室研究将用于量化有毒金属对微生物生长和抑制的影响，以便纳入预测模型。模拟工作将首次整合我们的知识，合养联合体的生物转化动力学，剂量依赖的抑制，以及扩散运输机制下氧化还原前沿形成的时空动力学。拟议活动产生的更广泛影响：虽然研究重点是历史上受到金属污染的LCDA沉积物中的微生物群落，但随着全球工业化程度的提高，环境与人类污染物的相互作用已成为美国和国际社会更重要的科学和社会问题。该项目集研究生、博士后助理和研究人员的研究指导和培训为一体。为本科生提供的研究经验补充助学金将用于将本科生纳入研究。结果将发表在一些高质量的同行评议的期刊文章上，并将通过在地方监管和公开会议以及国内和国际会议上的陈述向公众传达。将开发一个为科学家和非技术读者编写的因特网网站。这项研究完成后，将大大扩展对金属关键生物地球化学过程的基本和定量理解。该项目有可能建议金属生物修复技术的根本改进，因为结果将广泛适用于支持创新的生物战略，以减少金属污染场地对人类健康的风险和环境破坏。

0420374PeytonHeavy metals are highly toxic in the environment and their presence in sediments of Lake Coeur d'Alene (LCdA) in Idaho is mainly the result of historical mining in the mountains upstream. The objectives of this project are to 1) characterize the diversity of microorganisms in LCdA sediments using modern molecular biology techniques, 2) quantify the role of individual members of the microbial community in biogeochemical cycling of metals (Cu, Pb, and Zn), and 3) develop a dynamic numeric biogeochemical model of heavy metal cycling in sediment systems, calibrated to the unique environments of LCdA. These objectives will be met while testing the following overall hypothesis:A complex and dynamic community of phylogenetically distinct and previously uncharacterized microorganisms is present in the historically metal-contaminated sediments of Lake Coeur d'Alene. In response to a toxic metal stress, metal-tolerant species will dominate metal-sensitive species present in the sediments, with temporal and spatial microbial distribution and diversity dependant on the metal type and concentration. Dynamic biogeochemical models that incorporate chemical transport and reaction with novel microbial stress/response relationships and community dynamics can be used to 1) integrate complex microbial and geochemical observations across spatial and temporal scales, and 2) better predict broad community level response and influence on toxic metal cycling.Intellectual merit of the proposed activity: This project will significantly improve the quantitative understanding of interaction and response of a sediment microbial community subjected to severe heavy metal stress. Project objectives will be achieved by sampling LCdA sediments and identifying microbial diversity based on both 16S rDNA and rpoB gene sequences. These molecular techniques greatly facilitate the study of microbes in their natural environments and will provide a rational platform to base observations of community response to toxic metal additions. Shifts in microbial populations after being subjected to metal-stress will be quantified using terminal-restriction fragment length polymorphism (T-RFLP). Focused laboratory studies will be used to quantify the effects of toxic metals on microbial growth and inhibition for incorporation into the predictive model. The modeling effort will integrate for the first time to our knowledge, syntrophic consortium biotransformation dynamics, dose-dependent inhibition, and spatial and temporal dynamics of redox front formation under a diffusive transport regime. Broader impacts resulting from the proposed activity: While the research is focused on microbial communities in historically metal contaminated LCdA sediment, with increased industrialization worldwide, interactions of the environment and human contaminants have become more important issues, scientifically and socially, to the U.S. and internationally. The project integrates research mentoring and training of graduates, postdoctoral associate, and a research faculty. A supplemental grant for research experiences for undergraduates will be used to integrate undergraduate students into the research. The results will be published in a number of quality peer reviewed journal articles and will be conveyed to the public through presentations at local regulatory and public meetings, and at national and international conferences. An internet web site written for both scientists and non-technical readers will be developed. When complete, this research will significantly expand the fundamental and quantitative understanding of key biogeochemical processes for metals. The project has the potential to suggest fundamental improvements in metals-bioremediation technologies, since results will be broadly applicable in supporting innovative biological strategies to reduce human health risks and environmental damage from metal contaminated sites