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PI-Submitted Research Highlights for
Subsurface Biogeochemical Research Program

A Novel Iron-Loving Bacterium from the Deep Subsurface

Kenneth M. Kemner

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16 February 2017

New research has uncovered the bacterium Orenia metallireducens, a microorganism from 2 km deep underground capable of reducing iron.

The Science                        
A novel microorganism capable of withstanding high temperatures and briny water was isolated from a geological formation located two kilometers deep within the Illinois Basin. This bacterium, dubbed Orenia metallireducens, has many distinctive properties that allow it to reduce iron minerals such as goethite and hematite. These findings expand current knowledge of how bacteria survive in the deep, hostile environments of the terrestrial subsurface and provide further insights into how life might exist on other planetary bodies.

The Impact
The discovery of O. metallireducens expands current knowledge of the metabolic diversity of bacteria that inhabit the subsurface. Previously thought to be largely sterile, researchers now know that microbial life dwells deep within the fractures and pore spaces of rocks that make up Earth’s crust. These bacteria drive many of the biogeochemical cycles that occur within the subsurface, driving the dissolution and precipitation of minerals as well as the breakdown of organic matter. Understanding the microbially driven mechanisms behind these geochemical transformations is essential for parameterizing Earth system models that seek to quantify the flux of carbon between the atmosphere, soil, and subsurface.

Summary
The microbial reduction of ferric iron minerals is widespread in both terrestrial and marine environments and is potentially one of the earliest forms of metabolisms to evolve on Earth. Due to the abundance of ferric iron minerals in Earth’s crust, [Fe(III)] reduction is of global environmental significance, particularly in the subsurface where it contributes to water quality, contaminant fate and transport, and the biogeochemical cycling of carbon. Taking groundwater that was sampled from two kilometers deep underground, researchers isolated a novel member of the phylum Firmicutes, named Orenia metallireducens strain Z6. They found Ometallireducens to have numerous unique properties, including the ability to reduce ferric iron minerals across a broad range of temperature, pH, and salinity. Ometallireducens also lacks the c-type cytochromes that are typically present in bacteria capable of reducing ferric iron such as Geobacter and Shewanella species. The researchers also found that Ometallireducens is the only member of the order Halanaerobiales capable of reducing crystalline iron minerals such as goethite and hematite. This study’s results significantly expand the scope of phylogenetic affiliations, metabolic capabilities, and catalytic mechanisms that are known for iron-reducing microorganisms.
 

Contacts
BER Program Manager
Dr. Roland F. Hirsch
Program Manager, U.S. Department of Energy Office of Science
roland.hirsch@science.doe.gov; 301-903-9009

Principal Investigator
Dr. Kenneth M. Kemner
Argonne National Laboratory
kemner@anl.gov; 630-252-1163

Funding
This research is part of the Subsurface Science Scientific Focus Area at Argonne National Laboratory (ANL), which is supported by the Subsurface Biogeochemical Research program of the Office of Biological and Environmental Research, within the U.S. Department of Energy (DOE) Office of Science. Use of the Electron Microscopy Center at ANL and the Advanced Photon Source is supported by the Office of Basic Energy Sciences, within DOE’s Office of Science. MRCAT/EnviroCAT operations are supported by DOE and the MRCAT/EnviroCAT member institutions. All work at ANL was performed under contract DE-AC02-06CH11357. This work, including the efforts of Y. Dong, R. A. Sanford, R. A. Locke, Jr., and B. W. Fouke, was funded under Contract DE-FC26-05NT42588. Parts of this work, including the efforts of Y. Dong, R. A. Sanford, J. Y. Chang, and B. W. Fouke, were also funded by National Aeronautics and Space Administration (NNA13AA91A).

Publication
Dong, Y., R. A. Sanford, M. I. Boyanov, K. M. Kemner, T. M. Flynn, E. J. O’Loughlin, Y.-J. Chang, R. A. Locke Jr., J. R. Weber, S. M. Egan, R. I. Mackie, I. Cann, and B. W. Fouke. “Orenia metallireducens sp. nov. strain Z6, a novel metal-reducing member of the phylum Firmicutes from the deep subsurface.” Applied and Environmental Microbiology 82(21), 6440–53 (2016). [DOI:10.1128/AEM.02382-16].

Related Links
Subsurface Science Scientific Focus Area at Argonne National Laboratory

This research is part of the Subsurface Science Scientific Focus Area at Argonne National Laboratory, which is supported by the DOE Subsurface Biogeochemical Research Program, Office of Biological and Environmental Research, Office of Science. Use of the Electron Microscopy Center at Argonne and the Advanced Photon Source is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. MRCAT/EnviroCAT operations are supported by DOE and the MRCAT/EnviroCAT member institutions. All work at Argonne was performed under Contract DE-AC02-06CH11357. This work, including the efforts of Yiran Dong, Robert A. Sanford, Randall A. Locke, Jr., and Bruce W. Fouke, was funded by U.S. Department of Energy (DOE) (DE-FC26-05NT42588). Parts of this work, including the efforts of Yiran Dong, Robert A. Sanford, Janet Y. Chang, and Bruce Fouke, was also funded by National Aeronautics and Space Administration (NASA) (NNA13AA91A).

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