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.

化学物质甲基汞是有毒的环境污染物，在鱼类中含量很高。这导致了许多鱼类消费建议。虽然我们知道这种化学物质可以由微生物产生，将汞从无毒形式转变为有毒形式，但关于这种情况在环境中发生的位置仍存在许多问题。该项目的目标是确定哪些微生物可以在湖泊中进行这种反应。该研究将重点关注这些微生物在甲基汞含量高的鱼类活跃的湖泊中的高分辨率绘图。这些图谱将与最先进的宏基因组技术进行比较，将活性与甲基汞的产生联系起来。水资源管理者、监管机构、苗族自给渔民和其他利益相关者将参与进来，以加深对甲基汞造成的潜在威胁的了解。这项工作的成功完成将有助于更好地了解怜悯甲基化，并做出更明智的决策，以尽量减少人类接触受污染的鱼类。甲基汞 (MeHg) 是一种备受关注的环境污染物，因为它是一种神经毒素，在水生食物网中生物累积，导致人类通过鱼类消费而接触甲基汞。主要由于人类活动导致无机汞进入生态系统后，微生物将其转化为毒性更大的甲基汞。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之间，包括那些很少或没有培养代表的微生物谱系。这些新生物在甲基化中的作用几乎完全未被探索。实地研究将与美国地质调查局合作在两个截然不同的现场进行：威斯康星州麦迪逊的门多塔湖和爱达荷州地狱峡谷蛇河沿岸的一系列水库。两者都是高度富营养化的，初级生产是由农业养分输入推动的。迄今为止的研究表明，甲基汞在两个地点的温跃层下方积累。拟议的工作将通过追求三个具体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本测量水柱中空间和时间氧化还原梯度的甲基化和去甲基化率。目标 2 是使用宏基因组学和宏转录组学，使用鸟枪法测序群落 DNA 和 cDNA 以及计算分析，将甲基化基团与原位生物地球化学联系起来，以恢复群体基因组，同时将基因表达与各个功能组联系起来。将使用 qPCR 对关键群体进行定量，以提供甲基化器在时间和空间上的分布的更定量和可重复的视图。目标 3 是利用汞同位素的中生态孵化以及假设抑制或促进甲基化的针对性修正来定义甲基化的代谢限制。成功确定水柱中汞甲基化的存在将彻底改变我们对甲基汞动力学的理解，因为我们目前的理解是，这通常发生在厌氧沉积物中。通过对汞甲基化动态进行详细分析，控制甲基化和/或防止鱼类吸收的新方法可能成为可能。与当地苗族渔民社区的接触将通过增进对鱼类如何吸收甲基汞的了解来增加潜在效益。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.

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.

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.