Abstract
In nature, the bioaccumulative potent neurotoxin methylmercury (MeHg) is produced from inorganic mercury (Hg) predominantly by anaerobic microorganisms. Hg-contaminated soils are a potential source of MeHg due to microbial activity. We examine streambank soils collected from the contaminated East Fork Poplar Creek (EFPC) in Tennessee, USA, where seasonal variations in MeHg levels have been observed throughout the year, suggesting active microbial Hg methylation. In this study, we characterized the microbial community in contaminated bank soil samples collected from two locations over a period of one year and compared the results to soil samples from an uncontaminated reference site with similar geochemistry (n = 12). Microbial community composition and diversity were assessed by 16S rRNA gene amplicon sequencing. Furthermore, to isolate potential methylators from soils, enrichment cultures were prepared using selective media. A set of three clade-specific primers targeting the gene hgcA were used to detect Hg methylators among the δ-Proteobacteria in EFPC bank soils across all seasons. Two families among the δ-Proteobacteria that have been previously associated with Hg methylation, Geobacteraceae and Syntrophobacteraceae, were found to be predominant with relative abundances of 0.13% and 4.0%, respectively. However, in soil enrichment cultures, Firmicutes were predominant among families associated with Hg methylation. Specifically, Clostridiaceae and Peptococcaceae and their genera Clostridium and Desulfosporosinus were among the ten most abundant genera with relative abundances of 2.6% and 1.7%, respectively. These results offer insights into the role of microbial communities on Hg transformation processes in contaminated bank soils in EFPC. Identifying the biogeochemical drivers of MeHg production is critical for future remediation efforts.
| Original language | English |
|---|---|
| Article number | 31 |
| Journal | Water, Air, & Soil Pollution |
| Volume | 232 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jan 2021 |
Funding
This research was supported by the US Department of Energy (DOE) and Savannah River Nuclear Solution (SRNS) under subcontract no. 0000403075 and in part by the US Department of Energy’s (DOE) Oak Ridge Office of Environmental Management (ORO-EM) and URS | CH2M Oak Ridge LLC (UCOR) under the Mercury Remediation Technology Development Program at Oak Ridge National Laboratory (ORNL). ORNL is managed by UT-Battelle, LLC, for the US DOE under contract no. DE-AC05-00OR22725. We are grateful to Dr. Wendell McElhenney, at Tuskegee University for his generous help with statistical analyses. Notice: This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ). This research was supported by the US Department of Energy (DOE) and Savannah River Nuclear Solution (SRNS) under subcontract no. 0000403075 and in part by the US Department of Energy?s (DOE) Oak Ridge Office of Environmental Management (ORO-EM) and URS | CH2M Oak Ridge LLC (UCOR) under the Mercury Remediation Technology Development Program at Oak Ridge National Laboratory (ORNL). ORNL is managed by UT-Battelle, LLC, for the US DOE under contract no. DE-AC05-00OR22725. We are grateful to Dr. Wendell McElhenney, at Tuskegee University for his generous help with statistical analyses.
Keywords
- Clostridia
- Deltaproteobacteria
- Geochemistry
- Mercury methylation
- Methylmercury