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Title: Orenia metallireducens sp. nov. strain Z6, a Novel Metal-reducing Firmicute from the Deep Subsurface

A novel halophilic and metal-reducing bacterium,Orenia metallireducensstrain Z6, was isolated from briny groundwater extracted from a 2.02 km-deep borehole in the Illinois Basin, IL. This organism shared 96% 16S rRNA gene similarity withOrenia marismortui, but demonstrated physiological properties previously unknown for this genus. In addition to exhibiting a fermentative metabolism typical of genusOrenia, strain Z6 reduces various metal oxides [Fe(III), Mn(IV), Co(III), and Cr(VI)] using H2as the electron donor. Strain Z6 actively reduced ferrihydrite over broad ranges of pH (6-9.6), salinity (0.4-3.5 M NaCl) and temperature (20-60 °C). At pH 6.5, strain Z6 also reduced more crystalline iron oxides such as lepidocrocite (γ-FeOOH), goethite (α-FeOOH) and hematite (α-Fe2O3). Analysis of X-ray absorption fine structure (XAFS) following Fe(III) reduction by strain Z6 revealed spectra from ferrous secondary mineral phases consistent with the precipitation of vivianite [Fe3(PO4)2] and siderite (FeCO3). The draft genome assembled for strain Z6 is 3.47 Mb in size and contains 3,269 protein-coding genes. Unlike the well understood iron-reducingShewanellaandGeobacterspecies, this organism lacks thec-type cytochromes for typical Fe(III) reduction. Strain Z6 represents the first bacterial species in the genusOrenia(orderHalanaerobiales) reported to reduce ferric iron minerals and other metal oxides. This microbe expands both the phylogenetic and physiological scope of iron-reducingmore » microorganisms known to inhabit the deep subsurface and suggests new mechanisms for microbial iron reduction. These distinctions from otherOreniaspp. support the designation of strain Z6 as a new species,Orenia metallireducenssp. nov. ImportanceA novel iron-reducing species,Orenia metallireducenssp. nov. strain Z6, was isolated from groundwater collected from a geological formation located 2.02 kilometers below land surface in the Illinois Basin, USA. Phylogenetic, physiologic and genomic analyses of strain Z6 found it to have unique properties for iron reducers including: 1) active microbial iron-reducing capacity under a broad range of temperature (20-60 °C), pH (6-9.6), and salinity (0.4-3.5 M NaCl); 2) lack ofc-type cytochromes typically affiliated with iron reduction inGeobacterandShewanellaspecies; and 3) the only member of theHalanaerobialescapable of reducing crystalline goethite and hematite. This study expands the scope of phylogenetic affiliations, metabolic capacities, and catalytic mechanisms for iron-reducing microbes.« less
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Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied and Environmental Microbiology; Journal Volume: 82; Journal Issue: 21
American Society for Microbiology
Research Org:
Argonne National Laboratory (ANL)
Sponsoring Org:
USDOE Office of Science - Office of Biological and Environmental Research - Subsurface Biogeochemical Research; National Aeronautic and Space Administration (NASA)
Country of Publication:
United States