title: An autotrophic H2 -oxidizing, nitrate-respiring, Tc(VII)-reducing Acidovorax sp. isolated from a subsurface oxic-anoxic transition zone.
abstract: Increasing concentrations of H2 with depth were observed across a geologic unconformity and associated redox transition zone in the subsurface at the Hanford Site in south-central Washington, USA. An opposing gradient characterized by decreasing O2 and nitrate concentrations was consistent with microbial-catalysed biogeochemical processes. Sterile sand was incubated in situ within a multilevel sampler placed across the redox transition zone to evaluate the potential for Tc(VII) reduction and for enrichment of H2 -oxidizing denitrifiers capable of reducing Tc(VII). H2 -driven TcO4 (-) reduction was detected in sand incubated at all depths but was strongest in material from a depth of 17.1 m. Acidovorax spp. were isolated from H2 -nitrate enrichments from colonized sand from 15.1 m, with one representative, strain JHL-9, subsequently characterized. JHL-9 grew on acetate with either O2 or nitrate as electron acceptor (data not shown) and on medium with bicarbonate, H2 and nitrate. JHL-9 also reduced pertechnetate (TcO4 (-) ) under denitrifying conditions with H2 as the electron donor. H2 -oxidizing Acidovorax spp. in the subsurface at Hanford and other locations may contribute to the maintenance of subsurface redox gradients and offer the potential for Tc(VII) reduction.
authors.affiliation: Pacific Northwest National Laboratory, Richland, WA, 99352, USA.
authors.forename: Ji-Hoon
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Pacific Northwest National Laboratory, Richland, WA, 99352, USA.
authors.forename: James K
authors.initials: JK
authors.lastname: Fredrickson
authors.affiliation: Pacific Northwest National Laboratory, Richland, WA, 99352, USA.
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Plymale
authors.affiliation: Pacific Northwest National Laboratory, Richland, WA, 99352, USA.
authors.forename: Alice C
authors.initials: AC
authors.lastname: Dohnalkova
authors.affiliation: Pacific Northwest National Laboratory, Richland, WA, 99352, USA.
authors.forename: Charles T
authors.initials: CT
authors.lastname: Resch
authors.affiliation: Pacific Northwest National Laboratory, Richland, WA, 99352, USA.
authors.forename: James P
authors.initials: JP
authors.lastname: McKinley
authors.affiliation: Pacific Northwest National Laboratory, Richland, WA, 99352, USA.
authors.forename: Liang
authors.initials: L
authors.lastname: Shi
mesh_terms: D052818:Autotrophic Processes; D042621:Comamonadaceae / Q000145:classification / Q000302:isolation & purification* / Q000378:metabolism*; D006859:Hydrogen / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism*; D010084:Oxidation-Reduction; D012988:Soil Microbiology; D013667:Technetium / Q000378:metabolism*; D014861:Washington
chemical_list: D009566:Nitrates; D013667:Technetium; D006859:Hydrogen