Tracing the Uptake of Hg(II) in an Iron-Reducing Bacterium Using Mercury Stable Isotopes,Environmental Science & Technology Letters

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Tracing the Uptake of Hg(II) in an Iron-Reducing Bacterium Using Mercury Stable Isotopes
Environmental Science & Technology Letters ( IF 8.9 ) Pub Date : 2020-06-24 , DOI: 10.1021/acs.estlett.0c00409
Yuwei Wang ₁ , Sarah E. Janssen ₂ , Jeffra K. Schaefer ₁ , Nathan Yee ₁ , John R. Reinfelder ₁

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Anaerobic microorganisms play a key role in the biological mercury (Hg) cycle due to their ability to produce bioaccumulative neurotoxic methylmercury (MeHg). However, despite recent advances, how bacteria accumulate inorganic Hg [Hg(II)] prior to methylation is largely unknown. In this study, we applied Hg stable isotopes to measure changes in cellular compartments of Geobacter sulfurreducens and a nonmethylating mutant strain to investigate intracellular transport of Hg(II). Both strains accumulated intracellular Hg(II) that was lower in δ²⁰²Hg relative to dissolved extracellular Hg(II), demonstrating mass-dependent fractionation during uptake. Hg reduction by the mutant strain (50% Hg concentration loss in 24 h) resulted in higher δ²⁰²Hg values of cellular Hg than in wild-type cells. Further observations showed increasing δ²⁰²Hg values in dissolved extracellular MeHg and Hg(II) but decreasing δ²⁰²Hg values of intracellular Hg(II) in wild-type G. sulfurreducens suggesting that external Hg pools may be the proximate source of Hg for methylation in this bacterium. This investigation demonstrates that cellular uptake is comprised of multiple processes and transformations that influence Hg(II) prior to methylation, which can impart distinct isotopic signatures to Hg(II) and MeHg pools in the environment.

中文翻译：

使用汞稳定同位素示踪铁还原细菌中Hg（II）的吸收

由于厌氧微生物能够产生生物累积性神经毒性甲基汞（MeHg），因此它们在生物汞（Hg）循环中起着关键作用。然而，尽管有最近的进展，但是在甲基化之前细菌如何积累无机汞[Hg（II）]仍然是未知的。在这项研究中，我们应用了Hg稳定同位素来测量减少硫杆菌的地理细胞和非甲基化突变菌株在细胞内的变化，以研究Hg（II）的细胞内转运。胞内积累汞（II），这是δ较低两种菌株²⁰²汞柱相对于溶解的细胞外汞（II），摄取期间演示质量依赖性分馏。汞减少由突变株（在24小时50％的汞浓度损失）导致更高的δ ²⁰²细胞Hg的Hg值要比野生型细胞高。进一步观察表明δ增加^202倍以溶解细胞外甲基汞和Hg（II）汞柱的值，但降低δ ^202个细胞内的汞（II）的野生型汞柱值G.硫还原表明外部汞池可以是汞的甲基化邻近源在这种细菌中。这项研究表明，细胞吸收是由甲基化之前影响Hg（II）的多个过程和转化组成的，这些过程和转化可以为环境中的Hg（II）和MeHg池赋予独特的同位素特征。

更新日期：2020-08-11

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