title: Aerobic and Anaerobic Thiosulfate Oxidation by a Cold-Adapted, Subglacial Chemoautotroph.
abstract: Geochemical data indicate that protons released during pyrite (FeS2) oxidation are important drivers of mineral weathering in oxic and anoxic zones of many aquatic environments, including those beneath glaciers. Oxidation of FeS2 under oxic, circumneutral conditions proceeds through the metastable intermediate thiosulfate (S2O3 (2-)), which represents an electron donor capable of supporting microbial metabolism. Subglacial meltwaters sampled from Robertson Glacier (RG), Canada, over a seasonal melt cycle revealed concentrations of S2O3 (2-) that were typically below the limit of detection, despite the presence of available pyrite and concentrations of the FeS2 oxidation product sulfate (SO4 (2-)) several orders of magnitude higher than those of S2O3 (2-). Here we report on the physiological and genomic characterization of the chemolithoautotrophic facultative anaerobe Thiobacillus sp. strain RG5 isolated from the subglacial environment at RG. The RG5 genome encodes genes involved with pathways for the complete oxidation of S2O3 (2-), CO2 fixation, and aerobic and anaerobic respiration with nitrite or nitrate. Growth experiments indicated that the energy required to synthesize a cell under oxygen- or nitrate-reducing conditions with S2O3 (2-) as the electron donor was lower at 5.1°C than 14.4°C, indicating that this organism is cold adapted. RG sediment-associated transcripts of soxB, which encodes a component of the S2O3 (2-)-oxidizing complex, were closely affiliated with soxB from RG5. Collectively, these results suggest an active sulfur cycle in the subglacial environment at RG mediated in part by populations closely affiliated with RG5. The consumption of S2O3 (2-) by RG5-like populations may accelerate abiotic FeS2 oxidation, thereby enhancing mineral weathering in the subglacial environment.
authors.affiliation: Department of Earth Sciences, Montana State University, Bozeman, Montana, USA.
authors.forename: Zoë R
authors.initials: ZR
authors.lastname: Harrold
authors.affiliation: Department of Earth Sciences, Montana State University, Bozeman, Montana, USA.
authors.forename: Mark L
authors.initials: ML
authors.lastname: Skidmore
authors.affiliation: Department of Biological Sciences, University of Cincinnati, Cincinnati, Ohio, USA.
authors.forename: Trinity L
authors.initials: TL
authors.lastname: Hamilton
authors.affiliation: Department of Microbiology and Immunology, Montana State University, Bozeman, Montana, USA.
authors.forename: Libby
authors.initials: L
authors.lastname: Desch
authors.affiliation: Department of Microbiology and Immunology, Montana State University, Bozeman, Montana, USA.
authors.forename: Kirina
authors.initials: K
authors.lastname: Amada
authors.affiliation: Department of Earth Sciences, Montana State University, Bozeman, Montana, USA.
authors.forename: Will
authors.initials: W
authors.lastname: van Gelder
authors.affiliation: Department of Earth Sciences, Montana State University, Bozeman, Montana, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Glover
authors.affiliation: Department of Geosciences, University of Wisconsin-Madison, Madison, Wisconsin, USA NASA Astrobiology Institute, Mountain View, California, USA.
authors.forename: Eric E
authors.initials: EE
authors.lastname: Roden
authors.affiliation: Department of Microbiology and Immunology, Montana State University, Bozeman, Montana, USA NASA Astrobiology Institute, Mountain View, California, USA eboyd@montana.edu.
authors.forename: Eric S
authors.initials: ES
authors.lastname: Boyd
mesh_terms: D000693:Anaerobiosis; D002170:Canada; D002245:Carbon Dioxide / Q000378:metabolism; D003080:Cold Temperature; D020869:Gene Expression Profiling; D046448:Ice Cover / Q000382:microbiology*; D007501:Iron / Q000378:metabolism; D008969:Molecular Sequence Data; D009566:Nitrates / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D010084:Oxidation-Reduction; D017422:Sequence Analysis, DNA; D013440:Sulfides / Q000378:metabolism; D013855:Thiobacillus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D013885:Thiosulfates / Q000378:metabolism*
chemical_list: D009566:Nitrates; D009573:Nitrites; D013440:Sulfides; D013885:Thiosulfates; C011342:pyrite; D002245:Carbon Dioxide; D007501:Iron