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开采增加，对生态系统造成了重大压力，即改变了污染物的命运。为了确保这些资源的妥善管理和野生动物和人类健康的保护，这是至关重要的，以进一步提高我们的能力，预测有毒物质的命运，并制定补救战略，在典型的加拿大景观和条件。在有毒金属中，汞（Hg）是一种全球优先污染物，因为其毒性最强的一甲基汞（MMHg）在食物网中具有生物放大作用，即使在加拿大北极地区等偏远地区也是如此。汞作为一种对人类健康有重大影响的化学品，其重要性在最近通过的《汞问题水俣公约》中得到了强调，该公约于2013年10月由包括加拿大在内的140多个国家签署，具有法律约束力。该条约要求政府机构具备监测影响全球汞运输和循环过程的能力。该提案将填补联合国环境规划署最新汞评估报告中强调的汞运输和循环相关知识的重要空白。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，甲基化和生物体吸收之间的联系。我的第二个目标是表征的多样性的耐汞策略在冷适应微生物和开发新的微生物为基础的生态系统服务的污染场地的生物修复。我的第三个目标是开发新的古代理跟踪汞在环境中的再活化，通过评估如何遗传编码的细菌抗性机制演变，以应对最近的变化，汞交付到生态系统。最后一个目标将有助于评估生态系统对汞沉积的反应所涉及的时间滞后，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.