Microbial controls of mercury geochemistry

我的研究项目是研究微生物如何控制污染物进入食物网。我研究微生物如何感知和转化金属，以及这些过程是如何演变的。虽然我对有毒金属（类金属）对生态系统健康的威胁有广泛的兴趣，但本提案的重点是汞（Hg）生物地球化学。在全球范围内，由于食物网中强效神经毒素甲基汞（MeHg）的生物放大作用，汞是一种优先污染物。微生物参与了控制环境中汞种类相对丰度的大多数反应。一些微生物催化汞（II）与其元素挥发形式汞(0)之间的相互转化，而另一些微生物催化甲基汞的产生和降解。这些反应的相对重要性在整个地球化学梯度中有所不同，从氧气到低氧化还原电位的产甲烷或硫化物环境。我的长期目标是确定过去和现在环境中汞地球化学的微生物控制。最近批准了环境署《水俣公约》（2017年），突显了汞作为一种对人类健康造成关注的化学品的持续重要性。该公约要求各国政府监管汞排放及其对环境的影响，并禁止向其他国家出口汞废物。在这种新的国际监管背景下，工业必须制定处理国内汞废物的解决方案。在接下来的5年里，我的项目将培训31名hqp，同时解决联合国环境规划署全球汞评估中发现的知识空白，并支持《水俣公约》的实施，即汞沉积、甲基化和生物体吸收之间的联系，决定空气、水、空气和土壤之间交换速率的参数，以及更好地表征水生生态系统对大气汞沉积反应的滞后。我的第一个目标是评估是否存在跨微生物分类群的汞生物利用度的普遍控制。我的第二个目标是确定厌氧微生物还原过程。我的第三个目标是开发历史汞沉积的基因组古代用物，并确定细菌金属抗性机制在多大程度上进化，以响应最近在大空间尺度上向生态系统输送金属的变化。事实上，制定有效的减少风险战略取决于全面了解有毒污染物对生态系统目前和过去的影响。

My research program investigates how microbes control the entry of contaminants into food webs. I study how microbes sense and transform metals and how such processes evolved. Although I am broadly interested in threats to ecosystem health that are associated with toxic metal(oid)s, this proposal focuses on mercury (Hg) biogeochemistry. Globally, Hg is a priority contaminant due to biomagnification of the potent neurotoxin methylmercury (MeHg) in food webs. Microbes are involved in most reactions controlling the relative abundance of Hg species in the environment. Some microbes catalyze the interconversion between Hg(II) and its elemental volatile form, Hg(0), while others catalyze the production and degradation of MeHg. The relative importance of such reactions varies throughout geochemical gradients, from oxic to low redox potential methanogenic or sulfidic environments. My long-term objective is to identify the microbial controls of Hg geochemistry in past and current environments. The continued importance of Hg as a chemical of concern to human health was underscored by the recent ratification of the UNEP Minamata convention (2017) that requires governments to regulate Hg emissions and their environmental impacts, and to ban the export of Hg waste to other countries. With this new international regulatory context, industries must develop solutions to deal with their domestic Hg waste. Over the next 5 years, my program will train 31 HQPs while addressing knowledge gaps identified in the UNEP Global Hg assessment and supporting implementation of the Minamata convention, namely the link between Hg deposition, methylation and uptake by organisms, the parameters that determine the rates of exchange between air, water, air and soil and a better characterization of the lag in aquatic ecosystem response to atmospheric mercury deposition. My first objective is to evaluate whether there are universal controls of Hg bioavailability across microbial taxa. My second objective is to determine anaerobic microbial reduction processes. My third objective aims to develop genomic paleo-proxies for historical Hg deposition and determine to which extent bacterial metal resistance mechanisms have evolved in response to recent changes in metal delivery to ecosystems over broad spatial scales. Indeed, the development of effective risk reduction strategies depends on a comprehensive understanding of the present and past effects of toxic pollutants on ecosystems.