Microbial controls of mercury cycling

目前正在发生的重大环境变化，加上对北方自然资源的日益开发，对生态系统造成了重大压力，即改变了污染物的命运。为了确保对这些资源进行健全的管理，保护野生动物和人类健康，至关重要的是提高我们预测有毒物质命运的能力，并在典型的加拿大景观和条件下制定补救战略。在有毒金属中，汞（Hg）是全球优先考虑的污染物，因为其毒性最强的形式一甲基汞（MMHg）在食物网中具有生物放大作用，即使在加拿大北极等偏远地区也是如此。最近通过了《关于汞的水俣公约》，这是一项具有法律约束力的条约，由包括加拿大在内的140多个国家于2013年10月签署，凸显了汞作为一种对人类健康造成重大关切的化学品的重要性。该条约要求政府机构具备监控影响全球汞运输和循环过程的能力。该提案将填补最近联合国环境规划署汞评估报告中强调的与汞运输和循环有关的重要知识空白。我的第一个目标是确定溶解有机物（DOM）如何影响汞和MMHg的生物利用度，以评估汞沉积、甲基化和生物体摄取之间的联系。我的第二个目标是表征冷适应微生物抗汞策略的多样性，并为污染场地的生物修复开发新的基于微生物的生态系统服务。我的第三个目标是开发新的古代用物，通过评估基因编码的细菌抗性机制是如何响应近期汞向生态系统输送的变化而进化的，从而跟踪汞在环境中的再迁移。最后一个目标将有助于评估生态系统对汞沉积反应的时间滞后，并预测汞排放减少后的恢复时间。

Major environmental changes now underway combined with increased exploitation of northern natural resources impose an important stress on ecosystems, namely by altering the fate of contaminants. To ensure sound management of these resources and protection of wildlife and human health, it is critical to further our ability to predict the fate of toxicants and to develop remediation strategies in typical Canadian landscapes and conditions. Among toxic metals, mercury (Hg) is a global priority contaminant due to the biomagnification of its most toxic form monomethylmercury (MMHg) in foodwebs, even in remote regions such as the Canadian Arctic. The importance of Hg as a chemical of major concern to human health was underscored by the recent adoption of the Minamata Convention on Mercury, a legally binding treaty signed in Oct 2013 by more than 140 countries including Canada. This treaty requires that government agencies be equipped to monitor processes affecting global Hg transport and cycling. This proposal will fill important gaps of knowledge related to Hg transport and cycling highlighted in the most recent UN Environmental Programme Hg assessment report. My first objective is to determine how dissolved organic matter (DOM) affects Hg and MMHg bioavailability to assess the link between Hg deposition, methylation and uptake by living organisms. My second objective is to characterize the diversity of Hg resistance strategies in cold-adapted microbes and develop new microbe-based ecosystem services for the bioremediation of contaminated sites. My third objective aims to develop new paleo-proxies that track Hg remobilization in the environment by evaluating how genetically encoded bacterial resistance mechanisms evolved in response to recent changes in Hg delivery to ecosystems. This last objective will contribute to evaluating the time lag involved in ecosystem responses to mercury deposition and predicting recovery time following the reduction in Hg emissions.