Curated in an international collaboration led by ORNL postdoc Caitlin Gionfriddo, Hg-MATE-Db provides tools and data for expanding insights into microbially mediated mercury (Hg) transformations in the environment
Hg-MATE-Db—the Hg-cycling Microorganisms in Aquatic and Terrestrial Ecosystems Database—houses resources for identifying mercury-cycling microbes from diverse environments, such as the tidal salt marsh seen here on Assateague Island in Maryland. Marsh sediments harbor highly diverse communities of mercury-methylating microorganisms and can be hot spots for methylmercury production. [Courtesy Smithsonian Environmental Research Center]
The Hg-cycling Microorganisms in Aquatic and Terrestrial Ecosystems Database (Hg-MATE-Db) contains resources for identifying microbes that can transform Hg into the airborne Hg0 and Hg2+ found in streams, lakes, and oceans and the neurotoxic methylmercury (MeHg) found in fish and other aquatic life. This first release of the database has tools for measuring Hg methylator abundance and diversity and the potential of these organisms to methylate Hg. Hg-MATE-Db can be used to identify key microbial producers of MeHg, and upcoming versions will provide tools for identifying microbes that can transform MeHg into Hg0 and Hg2+.
Microbes play a critical role in controlling which form of Hg is dominant in an environment. Produced by microbes, MeHg is the form most toxic to humans, especially to developing fetuses and children. It accumulates in the food web and is the predominant form found in fish and seafood. The net production of MeHg depends on the presence and activity of Hg-methylating microbes and the bioavailability of Hg species. Microbes that demethylate Hg (to Hg2+) or reduce it (to Hg0) can impact MeHg production. The Hg-MATE-Db provides resources to identify the major microbial players in Hg cycling in an environment. Understanding these microbially mediated dynamics is key to predicting how changes to an ecosystem’s microbiome may impact MeHg production.
Hg-MATE-Db provides an ongoing and up-to-date collated resource of Hg-cycling genes from pure culture and environmental datasets. This resource enables researchers to identify Hg-cycling microorganisms and compare findings to other environmental settings and datasets. As the database grows with community input, so too will knowledge of the microorganisms that drive Hg cycling. Such microbes include those with the hgcAB gene pair that can produce MeHg, those that have genes of the mer operon that can demethylate or reduce Hg species as part of a detoxification pathway, and those with the mer operon that are resistant to Hg and can affect the form of Hg in the environment. Future versions of Hg-MATE-Db will include hgcAB sequences from targeted gene studies, further expanding insight into the gene pair’s diversity across environmental settings. Developers also plan to add a mer dataset to the database, which will contain resources for identifying genes of the mer operon that encode for demethylation of organic Hg species (merB), as well as genes involved in reducing inorganic Hg (merA), operon regulation (merR), and Hg transport across the cell (merTPC).
Gionfriddo, C., E. Capo, B. Peterson, H. Lin, D. Jones, A. G. Bravo, S. Bertilsson, J. Moreau, K. McMahon, D. A. Elias, and C. Gilmour. 2021. “Hg-MATE-Db.v1.01142021.” [Dataset]. The Smithsonian Institution. DOI:10.25573/serc.13105370.v1.
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