Unrecognized microbial sources of methyl mercury in freshwater lakes

淡水湖中未被识别的甲基汞微生物来源

• 批准号: 1935173
• 负责人: Katherine McMahon
• 金额: $ 32.96万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-05-15 至 2024-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1935173&HistoricalAwards=false
• 关键词: Unrecognized; microbial; sources; methyl; mercury

The chemical methylmercury is toxic environmental pollutant that can be found in high concentrations in fish. This has led to numerous fish consumption advisories. While we know that this chemical can be produced by microorganisms that change mercury from a non-toxic form into a toxic form, there are many questions concerning where this occurs in the environment. The goal of this project is to identify which microorganisms can perform this reaction in lakes. The study will focus on high resolution mapping where these microorganisms are active in lakes that have fish with high levels of methylmercury. These maps will be compared with state-of-the-science metagenomics techniques link activity to methylmercury production. Water managers, regulatory agencies, Hmong subsistence fishers, and other stakeholders will be engaged to increase understanding of the potential threat methylmercury poses. Successful completion of this work will lead to a better understanding of mercy methylation and lead to more informed decision making to minimize human exposure to contaminated fish.Methylmercury (MeHg) is an environmental pollutant of major concern due to its role as a neurotoxin that bioaccumulates in aquatic food webs, leading to human exposure through fish consumption. After inorganic mercury enters ecosystems due mainly to human activity, microbes are responsible for transforming it into the much more toxic MeHg. Preliminary data suggests that mercury methylation genes are distributed within and across divergent microbial lineages, including those with few or no cultured representatives. The role of these novel organisms in methylation is almost completely unexplored. Filed studies will be performed in collaboration with the US Geological Survey at two contrasting field sites: Lake Mendota in Madison, WI and a series of reservoirs along the Snake River in Hell's Canyon, Idaho. Both are highly eutrophic with primary production being fueled by agricultural nutrient input. Work to date has shown that MeHg accumulates just below the thermocline at both sites. The proposed work will build on these observations by pursuing three specific aims: Aim 1 is to measure methylation and demethylation rates across spatial and temporal redox gradients in the water column using samples collected from the study sites. Aim 2 is to link methylator guilds to in situ biogeochemistry using metagenomics and metatranscriptomics using shotgun sequencing community DNA and cDNA and computational analysis to recover population genomes while linking gene expression to individual functional groups. Key populations will be quantified using qPCR to provide a more quantitative and replicated view of the methylator distributions in time and space. Aim 3 is to define metabolic constraints on methylation using mesocosm incubations with mercury isotopes and targeted amendments hypothesized to inhibit or promote methylation. Successfully establishing the presence of mercury methylation in the water column would be transformative to our understanding of MeHg dynamics, as our current understanding is that this normally occurs in anaerobic sediments. By providing detailed analysis of Hg methylation dynamics, new approaches to controlling methylation and/or preventing uptake in fish may be possible. Outreach to a local Hmong community of fishers will increase the potential benefits by increasing understanding of how MeHg is take up by fish.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

化学甲基马凝是有毒的环境污染物，可以在鱼类中高浓度发现。这导致了许多鱼类消费咨询。虽然我们知道这种化学物质可以由微生物从无毒形式转变为有毒形式的微生物产生，但有关环境中的何处存在许多问题。该项目的目的是确定哪些微生物可以在湖泊中进行这种反应。该研究将集中于高分辨率映射，其中这些微生物在具有高水平甲基汞的鱼的湖泊中活跃。这些地图将与科学的宏基因组学技术与甲基汞生产联系起来。水管理人员，监管机构，苗族维持生计渔民和其他利益相关者将敬业，以增进对甲基汞姿势的潜在威胁的了解。成功完成这项工作将使人们更好地了解慈悲甲基化，并导致更明智的决策，以最大程度地减少人类对被污染的鱼类的接触。Methylmercury（MEHG）是一种主要关注的环境污染物，因为它作为神经毒素作为一种神经毒素的作用，可通过生物毒素在水上食品网中进行生物积累，从而导致人类通过鱼类消费量，从而导致人类的水生毒素。无机汞进入主要由于人类活动的生态系统之后，微生物负责将其转化为更具毒性的MEHG。初步数据表明，汞甲基化基因分布在不同的微生物谱系内和跨不同的微生物谱系中，包括那些较少或没有培养的代表的人。这些新生物在甲基化中的作用几乎完全没有探索。提交的研究将与美国地质调查局合作在两个对比的田野上合作：威斯康星州麦迪逊市的门道塔湖和爱达荷州地狱峡谷的Snake River沿线的一系列水库。两者都是高度富营养化的，主要生产受到农业营养投入的推动。迄今为止的工作表明，MEHG在两个站点的热跃层下方都累积。拟议的工作将通过追求三个特定目标来建立在这些观察结果的基础上：目标1是使用从研究地点收集的样品在水柱中的空间和颞氧化还原梯度之间进行甲基化和脱甲基化速率。 AIM 2是使用宏基因组学和元文字组学使用shot弹枪测序社区DNA和cDNA和计算分析将甲基甲基公会与原位生物地球化学联系起来，以恢复种群基因组，同时将基因表达与单个功能组联系起来。将使用QPCR量化关键种群，以在时空中对甲基分布进行更定量和复制的视图。目的3是使用中验与汞同位素孵育和靶向修正案抑制以抑制或促进甲基化的靶向修正案来定义甲基化的代谢约束。成功地在水柱中建立汞甲基化的存在将是我们对MEHG动力学的理解的影响，因为我们目前的理解是，这通常发生在厌氧沉积中。通过对HG甲基化动态提供详细的分析，可以进行控制甲基化和/或防止鱼类摄取的新方法。向当地的苗族渔民社区的宣传将通过提高对FISH的MEHG的了解来提高潜在的好处。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子和更广泛影响的评估评估的评估来支持的。

项目成果

Environmental formation of methylmercury is controlled by synergy of inorganic mercury bioavailability and microbial mercury‐methylation capacity

甲基汞的环境形成受无机汞生物利用度和微生物汞甲基化能力的协同控制

• DOI: 10.1111/1462-2920.16364
• 发表时间: 2023
• 期刊: Environmental Microbiology
• 影响因子: 5.1
• 作者: Peterson, Benjamin D.;Krabbenhoft, David P.;McMahon, Katherine D.;Ogorek, Jacob M.;Tate, Michael T.;Orem, William H.;Poulin, Brett A.
• 通讯作者: Poulin, Brett A.

Mercury Methylation Genes Identified across Diverse Anaerobic Microbial Guilds in a Eutrophic Sulfate-Enriched Lake

• DOI: 10.1021/acs.est.0c05435
• 发表时间: 2020-12-15
• 期刊: ENVIRONMENTAL SCIENCE & TECHNOLOGY
• 影响因子: 11.4
• 作者: Peterson, Benjamin D.;McDaniel, Elizabeth A.;McMahon, Katherine D.
• 通讯作者: McMahon, Katherine D.

Expanded Phylogenetic Diversity and Metabolic Flexibility of Mercury-Methylating Microorganisms

• DOI: 10.1128/msystems.00299-20
• 发表时间: 2020-07-01
• 期刊: MSYSTEMS
• 影响因子: 6.4
• 作者: McDaniel, Elizabeth A.;Peterson, Benjamin D.;McMahon, Katherine D.
• 通讯作者: McMahon, Katherine D.