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Title: Determining the Reliability of Measuring Mercury Cycling Gene Abundance with Correlations with Mercury and Methylmercury Concentrations

Abstract

Methylmercury (MeHg) is a bioaccumulative toxic contaminant in many ecosystems but factors governing its production are poorly understood. Recent work has shown that the anaerobic microbial conversion of mercury (Hg) to MeHg requires the Hg-methylation genes hgcAB and that these genes can be used as biomarkers in PCR-based estimators of Hg-methylator abundance. In an effort to determine reliable methods for assessing hgcA abundance and diversity and linking it to MeHg concentrations, multiple approaches were compared including metagenomic shotgun sequencing, 16S rRNA gene pyrosequencing and cloning/sequencing hgcAB gene products. Hg-methylator abundance was also determined by quantitative hgcA qPCR amplification and metaproteomics for comparison to the above measurements. Samples from eight Hg-contaminated sites were examined over a range of total Hg (HgT; 0.03–14 mg kg-1 wet wt. soil) and MeHg (0.05–27 µg kg-1 wet wt. soil) concentrations. In the metagenome and amplicon sequencing of hgcAB diversity, the Deltaproteobacteria were the dominant Hg-methylators, while Firmicutes and methanogenic Archaea were typically ~50% less abundant. This was consistent with metaproteomics estimates where the Deltaproteobacteria were consistently higher. The 16S rRNA gene pyrosequencing did not have sufficient resolution to identify hgcAB+ species. Metagenomic and hgcAB results were similar for Hg-methylator diversity and showed a tractable relationshipmore » between Hg-methylating bacteria and soil Hg concentrations among similar environmental samples. However, clade-specific qPCR-based approaches for hgcA are only appropriate when comparing the abundance of a particular clade across various samples.« less

Authors:
 [1];  [1];  [1];  [1];  [2];  [3];  [4]; ORCiD logo [4];  [5];  [1];  [1];  [1];  [1];  [1];  [6];  [6];  [7];  [8];  [9]
  1. Oak Ridge National Laboratory
  2. Troy State University
  3. Texas A & M University
  4. BATTELLE (PACIFIC NW LAB)
  5. ORNL
  6. Montana State University
  7. University of Missouri, Columbia
  8. Smithsonian Enviromental Research Center
  9. OAK RIDGE NATIONAL LAB
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1572494
Report Number(s):
PNNL-SA-145153
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Environmental Science & Technology
Additional Journal Information:
Journal Volume: 53; Journal Issue: 15
Country of Publication:
United States
Language:
English
Subject:
microbial community, PCR, qPCR, Metagenome, hgcAB, 16s sequencinv

Citation Formats

Christensen, Geoffrey A., Gionfriddo, Caitlin M., King, Andrew J., Moberly, James G., Miller, Carrie, Somenahally, Anil C., Callister, Stephen J., Brewer, Heather M., Podar, Mircea, Brown, Steven D., Palumbo, Anthony V., Brandt, Craig C., Wymore, Ann M., Brooks, Scott C., Hwang, C, Fields, Matthew W., Wall, Judy D., Gilmour, Cynthia C., and Elias, Dwayne A. Determining the Reliability of Measuring Mercury Cycling Gene Abundance with Correlations with Mercury and Methylmercury Concentrations. United States: N. p., 2019. Web. doi:10.1021/acs.est.8b06389.
Christensen, Geoffrey A., Gionfriddo, Caitlin M., King, Andrew J., Moberly, James G., Miller, Carrie, Somenahally, Anil C., Callister, Stephen J., Brewer, Heather M., Podar, Mircea, Brown, Steven D., Palumbo, Anthony V., Brandt, Craig C., Wymore, Ann M., Brooks, Scott C., Hwang, C, Fields, Matthew W., Wall, Judy D., Gilmour, Cynthia C., & Elias, Dwayne A. Determining the Reliability of Measuring Mercury Cycling Gene Abundance with Correlations with Mercury and Methylmercury Concentrations. United States. doi:10.1021/acs.est.8b06389.
Christensen, Geoffrey A., Gionfriddo, Caitlin M., King, Andrew J., Moberly, James G., Miller, Carrie, Somenahally, Anil C., Callister, Stephen J., Brewer, Heather M., Podar, Mircea, Brown, Steven D., Palumbo, Anthony V., Brandt, Craig C., Wymore, Ann M., Brooks, Scott C., Hwang, C, Fields, Matthew W., Wall, Judy D., Gilmour, Cynthia C., and Elias, Dwayne A. Tue . "Determining the Reliability of Measuring Mercury Cycling Gene Abundance with Correlations with Mercury and Methylmercury Concentrations". United States. doi:10.1021/acs.est.8b06389.
@article{osti_1572494,
title = {Determining the Reliability of Measuring Mercury Cycling Gene Abundance with Correlations with Mercury and Methylmercury Concentrations},
author = {Christensen, Geoffrey A. and Gionfriddo, Caitlin M. and King, Andrew J. and Moberly, James G. and Miller, Carrie and Somenahally, Anil C. and Callister, Stephen J. and Brewer, Heather M. and Podar, Mircea and Brown, Steven D. and Palumbo, Anthony V. and Brandt, Craig C. and Wymore, Ann M. and Brooks, Scott C. and Hwang, C and Fields, Matthew W. and Wall, Judy D. and Gilmour, Cynthia C. and Elias, Dwayne A.},
abstractNote = {Methylmercury (MeHg) is a bioaccumulative toxic contaminant in many ecosystems but factors governing its production are poorly understood. Recent work has shown that the anaerobic microbial conversion of mercury (Hg) to MeHg requires the Hg-methylation genes hgcAB and that these genes can be used as biomarkers in PCR-based estimators of Hg-methylator abundance. In an effort to determine reliable methods for assessing hgcA abundance and diversity and linking it to MeHg concentrations, multiple approaches were compared including metagenomic shotgun sequencing, 16S rRNA gene pyrosequencing and cloning/sequencing hgcAB gene products. Hg-methylator abundance was also determined by quantitative hgcA qPCR amplification and metaproteomics for comparison to the above measurements. Samples from eight Hg-contaminated sites were examined over a range of total Hg (HgT; 0.03–14 mg kg-1 wet wt. soil) and MeHg (0.05–27 µg kg-1 wet wt. soil) concentrations. In the metagenome and amplicon sequencing of hgcAB diversity, the Deltaproteobacteria were the dominant Hg-methylators, while Firmicutes and methanogenic Archaea were typically ~50% less abundant. This was consistent with metaproteomics estimates where the Deltaproteobacteria were consistently higher. The 16S rRNA gene pyrosequencing did not have sufficient resolution to identify hgcAB+ species. Metagenomic and hgcAB results were similar for Hg-methylator diversity and showed a tractable relationship between Hg-methylating bacteria and soil Hg concentrations among similar environmental samples. However, clade-specific qPCR-based approaches for hgcA are only appropriate when comparing the abundance of a particular clade across various samples.},
doi = {10.1021/acs.est.8b06389},
journal = {Environmental Science & Technology},
number = 15,
volume = 53,
place = {United States},
year = {2019},
month = {8}
}