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.

甲基汞是一种有毒的环境污染物，在鱼类中含量很高。这导致了大量的鱼类消费。虽然我们知道这种化学品可以由微生物产生，将汞从无毒形式变为有毒形式，但关于这种情况在环境中发生的位置还有很多问题。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。该研究将侧重于高分辨率绘图，这些微生物在有高甲基汞含量鱼类的湖泊中活跃。这些图谱将与将活动与甲基汞生产联系起来的最新科学宏基因组学技术进行比较。水资源管理人员、监管机构、苗族生计渔民和其他利益攸关方将参与进来，以提高对甲基汞潜在威胁的认识。这项工作的成功完成将使人们更好地了解汞的甲基化，并使人们做出更明智的决策，以尽量减少人类接触受污染的鱼类。甲基汞（MeHg）是一种主要的环境污染物，由于其作为神经毒素的作用，在水生食物网中生物积累，导致人类通过食用鱼类接触。无机汞主要由于人类活动进入生态系统后，微生物负责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，包括那些很少或没有培养的代表。这些新生物在甲基化中的作用几乎完全未被探索。将与美国地质调查局合作，在两个对比鲜明的现场进行实地研究：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着的一系列水库。两者都是高度富营养化的初级生产是由农业养分投入。迄今为止的工作表明，甲基汞在这两个地点的温跃层之下积累。拟议的工作将通过追求三个具体目标建立在这些观察的基础上：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。目的2是使用元基因组学和元转录组学将甲基化剂协会与原位生物化学联系起来，使用鸟枪测序社区DNA和cDNA以及计算分析来恢复群体基因组，同时将基因表达与个体功能组联系起来。将使用qPCR对关键群体进行定量，以提供时间和空间上甲基化子分布的更定量和重复视图。目的3是定义甲基化的代谢限制，使用围隔孵育汞同位素和有针对性的修正假设抑制或促进甲基化。成功地建立汞甲基化在水柱中的存在将是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。通过对汞甲基化动力学进行详细分析，有可能找到控制甲基化和/或防止鱼类摄入汞的新方法。对当地苗族渔民社区的宣传将通过增加对鱼类如何吸收甲基汞的了解来增加潜在的利益，该奖项反映了国家科学基金会的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来提供支持。

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.