title: Thiosulfate oxidation by Thiomicrospira thermophila: metabolic flexibility in response to ambient geochemistry.
abstract: Previous studies of the stoichiometry of thiosulfate oxidation by colorless sulfur bacteria have failed to demonstrate mass balance of sulfur, indicating that unidentified oxidized products must be present. Here the reaction stoichiometry and kinetics under variable pH conditions during the growth of Thiomicrospira thermophila strain EPR85, isolated from diffuse hydrothermal fluids at the East Pacific Rise, is presented. At pH 8.0, thiosulfate was stoichiometrically converted to sulfate. At lower pH, the products of thiosulfate oxidation were extracellular elemental sulfur and sulfate. We were able to replicate previous experiments and identify the missing sulfur as tetrathionate, consistent with previous reports of the activity of thiosulfate dehydrogenase. Tetrathionate was formed under slightly acidic conditions. Genomic DNA from T. thermophila strain EPR85 contains genes homologous to those in the Sox pathway (soxAXYZBCDL), as well as rhodanese and thiosulfate dehydrogenase. No other sulfur oxidizing bacteria containing sox(CD)2 genes have been reported to produce extracellular elemental sulfur. If the apparent modified Sox pathway we observed in T. thermophila is present in marine Thiobacillus and Thiomicrospira species, production of extracellular elemental sulfur may be biogeochemically important in marine sulfur cycling.
authors.affiliation: Department of Earth and Planetary Sciences, Washington University, St. Louis, MO, 63130, USA. jhoughton@levee.wustl.edu.
authors.forename: J L
authors.initials: JL
authors.lastname: Houghton
authors.affiliation: Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC, 20015, USA.
authors.forename: D I
authors.initials: DI
authors.lastname: Foustoukos
authors.affiliation: Biosciences Division, Argonne National Laboratory, Lemont, IL, 60439, USA.|Computation Institution, The University of Chicago, Chicago, IL, 60637, USA.
authors.forename: T M
authors.identifier: 0000-0002-1838-8942
authors.initials: TM
authors.lastname: Flynn
authors.affiliation: Department of Biochemistry and Microbiology and Institute of Earth, Ocean and Atmospheric Sciences, Rutgers University, New Brunswick, NJ, 08901, USA.
authors.forename: C
authors.initials: C
authors.lastname: Vetriani
authors.affiliation: Department of Earth and Planetary Sciences, Washington University, St. Louis, MO, 63130, USA.
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Bradley
authors.affiliation: Department of Earth and Planetary Sciences, Washington University, St. Louis, MO, 63130, USA.
authors.forename: D A
authors.initials: DA
authors.lastname: Fike
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D010084:Oxidation-Reduction; D010087:Oxides / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D013455:Sulfur / Q000378:metabolism; D013457:Sulfur Compounds / Q000378:metabolism; D013855:Thiobacillus / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D013885:Thiosulfates / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D010087:Oxides; D013457:Sulfur Compounds; D013885:Thiosulfates; C405951:sulfur monoxide; D013455:Sulfur; D010088:Oxidoreductases; C432587:thiosulfate dehydrogenase