DOE OSTI · 3375056
Hg Accumulation by Single-Cell Sulfate-Reducing Bacteria Methylating Mercury
Abstract
Methylmercury (MeHg) is a potent neurotoxin that poses risks to ecosystems and human health. MeHg is produced by microbes following saturating-like kinetics. We hypothesize that this saturation reflects a limited intracellular mercury (Hg) accumulation. Here, in this study, we investigated Hg accumulation in Pseudodesulfovibrio hydrargyri BerOc1, a sulfate-reducing model strain able to methylate Hg. Cells were incubated with 0.5 and 2 μM of mercury (HgCl 2 ), and mercury localization was studied using synchrotron-based nano-X-ray fluorescence and high-resolution analytical electron microscopy. For both concentrations, Hg was detected in the bacterial cytosol, in addition to extracellular (Hg, S)-containing nanoparticles. Intracellular Hg levels were slightly higher at 2 μM than at 0.5 μM (1.61 vs 1.40 pg.mm –2 ), suggesting a regulated accumulation. However, the population exhibited heterogeneity in Hg accumulation, particularly at the highest Hg exposure, with some cells being Hg hyperaccumulators. Correlative imaging between Hg localization and cell viability revealed that these hyperaccumulating cells were non-active. Our results suggest that active cells regulate Hg accumulation. From an analytical perspective, a minor subpopulation of hyperaccumulating cells can bias bulk measurements and should be considered in interpreting Hg accumulation in microorganisms. Environmentally, these cells can impact Hg cycling by acting as a metal sink.
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Le Gohalen, Antoine [Université de Pau et des Pays de l’Adour (UPPA) (France); Centre National de la Recherche Scientifique (CNRS), Pau (France). Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux (IPREM)], Goñi-Urriza, Marisol [Université de Pau et des Pays de l’Adour (UPPA) (France); Centre National de la Recherche Scientifique (CNRS), Pau (France). Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux (IPREM)] (ORCID:0000000176946511), Barrouilhet, Sophie [Université de Pau et des Pays de l’Adour (UPPA) (France); Centre National de la Recherche Scientifique (CNRS), Pau (France). Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux (IPREM)], Monperrus, Mathilde [Université de Pau et des Pays de l’Adour (UPPA) (France); Centre National de la Recherche Scientifique (CNRS), Pau (France). Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux (IPREM)] (ORCID:0000000263371672), Fernández-Monreal, Mónica [Université de Bordeaux (France). Bordeaux Imaging Center (BIC); Centre National de la Recherche Scientifique (CNRS), Bordeaux (France); Institut national de la santé et de la recherche médicale (Inserm), Bordeaux (France)], Pied, Noémie [Université de Bordeaux (France). Bordeaux Imaging Center (BIC); Centre National de la Recherche Scientifique (CNRS), Bordeaux (France); Institut national de la santé et de la recherche médicale (Inserm), Bordeaux (France)], Zaluzec, Nestor J. [Argonne National Laboratory (ANL), Argonne, IL (United States); University of Chicago, IL (United States); Western Sydney University, Parramatta, NSW (Australia)], Salome, Murielle [European Synchrotron Radiation Facility (ESRF), Grenoble (France)], Cloetens, Peter [European Synchrotron Radiation Facility (ESRF), Grenoble (France)], Bohic, Sylvain [European Synchrotron Radiation Facility (ESRF), Grenoble (France); University of Grenoble Alpes, Grenoble (France). Synchrotron Radiation for Biomedicine (STROBE); Institut national de la santé et de la recherche médicale (Inserm), Grenoble (France)] (ORCID:0000000163557592), Luo, Yanqi [Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)] (ORCID:0000000156249583), Chen, Si [Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)] (ORCID:0000000166192699), Isaure, Marie-Pierre [Université de Pau et des Pays de l’Adour (UPPA) (France); Centre National de la Recherche Scientifique (CNRS), Pau (France). Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux (IPREM)] (ORCID:0000000265575759). 2026-04-09. Hg Accumulation by Single-Cell Sulfate-Reducing Bacteria Methylating Mercury. https://doi.org/10.1021/acsearthspacechem.5c00368
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