title: In situ analysis of oxygen consumption and diffusive transport in high-temperature acidic iron-oxide microbial mats.
abstract: The role of dissolved oxygen as a principal electron acceptor for microbial metabolism was investigated within Fe(III)-oxide microbial mats that form in acidic geothermal springs of Yellowstone National Park (USA). Specific goals of the study were to measure and model dissolved oxygen profiles within high-temperature (65-75°C) acidic (pH = 2.7-3.8) Fe(III)-oxide microbial mats, and correlate the abundance of aerobic, iron-oxidizing Metallosphaera yellowstonensis organisms and mRNA gene expression levels to Fe(II)-oxidizing habitats shown to consume oxygen. In situ oxygen microprofiles were obtained perpendicular to the direction of convective flow across the aqueous phase/Fe(III)-oxide microbial mat interface using oxygen microsensors. Dissolved oxygen concentrations dropped from ∼ 50-60 μM in the bulk-fluid/mat surface to below detection (< 0.3 μM) at a depth of ∼ 700 μm (∼ 10% of the total mat depth). Net areal oxygen fluxes into the microbial mats were estimated to range from 1.4-1.6 × 10(-4)  μmol cm(-2)  s(-1) . Dimensionless parameters were used to model dissolved oxygen profiles and establish that mass transfer rates limit the oxygen consumption. A zone of higher dissolved oxygen at the mat surface promotes Fe(III)-oxide biomineralization, which was supported using molecular analysis of Metallosphaera yellowstonensis 16S rRNA gene copy numbers and mRNA expression of haem Cu oxidases (FoxA) associated with Fe(II)-oxidation.
authors.affiliation: Department of Chemical and Biological Engineering, Montana State University, Bozeman, MT 59717, USA.
authors.forename: Hans C
authors.initials: HC
authors.lastname: Bernstein
authors.forename: Jacob P
authors.initials: JP
authors.lastname: Beam
authors.forename: Mark A
authors.initials: MA
authors.lastname: Kozubal
authors.forename: Ross P
authors.initials: RP
authors.lastname: Carlson
authors.forename: William P
authors.initials: WP
authors.lastname: Inskeep
mesh_terms: D004058:Diffusion; D005290:Ferric Compounds / Q000032:analysis / Q000378:metabolism*; D019848:Gene Expression Regulation, Archaeal; D045482:Hot Springs / Q000737:chemistry / Q000382:microbiology*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D064307:Microbiota / Q000502:physiology*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D010100:Oxygen / Q000032:analysis; D010101:Oxygen Consumption / Q000502:physiology*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D011956:Receptors, Cell Surface / Q000235:genetics; D016943:Sulfolobaceae / Q000235:genetics / Q000378:metabolism*
chemical_list: D005290:Ferric Compounds; D012336:RNA, Ribosomal, 16S; D011956:Receptors, Cell Surface; C000499:ferric oxide; D010088:Oxidoreductases; D010100:Oxygen