B14C-03
Investigating the Connection between hgcA and Mercury Methylation Rates in the Environment
Monday, 14 December 2015: 16:30
2010 (Moscone West)
Andrew John King1, Geoff Alex Christensen2, Ann M Wymore3, Mircea Podar3, Richard A Hurt Jr.3, Steven D Brown3, Anthony V Palumbo2, Kelly S Bender4, Matthew W. Fields5, Cynthia C Gilmour6, Eugenio F U Santillan2, Craig C Brandt2 and Dwayne A Elias3, (1)Department of Energy Oak Ridge, Oak Ridge, TN, United States, (2)Oak Ridge National Laboratory, Oak Ridge, TN, United States, (3)Oak Ridge National Laboratory, Biosciences Division, Oak Ridge, TN, United States, (4)Southern Illinois University Carbondale, Carbondale, IL, United States, (5)Center for Biofilm Engineering, Bozeman, MT, United States, (6)Smithsonian Institution, Smithsonian Environmental Research Center, Edgewater, MD, United States
Abstract:
Methylmercury (MeHg) is a common contaminant in many natural environments and is known to be a neurotoxin that impacts human health through bioaccumulation in food webs. The anaerobic conversion of mercury (Hg) to MeHg by microorganisms requires the presence of both HgcA and HgcB. In an effort to link hgcAB abundance and diversity with MeHg generation rates, we performed metagenomic and 16S rRNA sequencing as well as qualitative polymerase chain reaction (qPCR) of hgcA on samples from eight mercury-contaminated sites ranging from tidal marshes to Arctic permafrost. Custom algorithms were developed to filter hgcA sequences from the metagenomes, and to then select for those lineages that also contained hgcB. In the metagenomes, the Deltaproteobacteria dominated the pool of hgcAB from all eight sites; however, Firmicutes and methanogenic Archaea were each 50% less abundant. In parallel to the metagenomics studies, clone libraries of hgcAB were constructed for each site. This more cost-effective approach allowed us to verify the identity of the hgcAB+ organism, and yielded similar results to the metagenomes. Additionally, to determine the accuracy of our new degenerate qPCR primer sets (three sets specific to the three major clades of mercury methylators) in the environment, qPCR hgcA abundance values were compared to those derived from the metagenomes. Finally, we present evidence that hgcA abundance can correlate with MeHg concentrations but that the relationship is influenced by local environmental conditions. Our work demonstrates the relative efficacy of genetic methods for assessing the presence of mercury-methylators in eight different environments contaminated with mercury as well as the strength of association between abundance of hgcA and the rate of mercury methylation.
