Tracing the uptake of Hg(II) in an iron-reducing bacterium using mercury stable isotopes

Yuwei Wang; Sarah E. Janssen; Jeffra K Schaefer; Nathan Yee; John R Reinfelder

doi:10.1021/acs.estlett.0c00409

Tracing the uptake of Hg(II) in an iron-reducing bacterium using mercury stable isotopes

Environmental Science and Technology Letters

By: Yuwei Wang, Sarah E. Janssen, Jeffra K Schaefer, Nathan Yee, and John R Reinfelder

https://doi.org/10.1021/acs.estlett.0c00409

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Abstract

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.

Additional publication details
Publication type	Article
Publication Subtype	Journal Article
Title	Tracing the uptake of Hg(II) in an iron-reducing bacterium using mercury stable isotopes
Series title	Environmental Science and Technology Letters
DOI	10.1021/acs.estlett.0c00409
Volume	7
Issue	8
Year Published	2020
Language	English
Publisher	American Chemical Society
Contributing office(s)	Upper Midwest Water Science Center
Description	6 p.
First page	573
Last page	578
Google Analytic Metrics	Metrics page