Chemotrophic microorganisms gain energy for cellular functions by catalyzing oxidation–reduction (redox) reactions that are out of equilibrium. Calculations of the Gibbs energy (
Microbial sulfur cycling in marine sediments often occurs in environments characterized by transient chemical gradients that affect both the availability of nutrients and the activity of microbes. High turnover rates of intermediate valence sulfur compounds and the intermittent availability of oxygen in these systems greatly impact the activity of sulfur‐oxidizing micro‐organisms in particular. In this study, the thiosulfate‐oxidizing hydrothermal vent bacterium
- NSF-PAR ID:
- 10460639
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Geobiology
- Volume:
- 17
- Issue:
- 5
- ISSN:
- 1472-4677
- Page Range / eLocation ID:
- p. 564-576
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Summary ) can identify whether a reaction is thermodynamically favourable and quantify the accompanying energy yield at the temperature, pressure and chemical composition in the system of interest. Based on carefully calculated values ofΔG r , we predict a novel microbial metabolism – sulfur comproportionation (3H2S +ΔG r + 2H+ ⇌ 4S0+ 4H2O). We show that at elevated concentrations of sulfide and sulfate in acidic environments over a broad temperature range, this putative metabolism can be exergonic ( <0), yielding ~30–50 kJ mol−1. We suggest that this may be sufficient energy to support a chemolithotrophic metabolism currently missing from the literature. Other versions of this metabolism, comproportionation to thiosulfate (H2S +ΔG r ⇌ + H2O) and to sulfite (H2S + 3 ⇌ 4+ 2H+), are only moderately exergonic or endergonic even at ideal geochemical conditions. Natural and impacted environments, including sulfidic karst systems, shallow‐sea hydrothermal vents, sites of acid mine drainage, and acid–sulfate crater lakes, may be ideal hunting grounds for finding microbial sulfur comproportionators. -
Abstract The degassing of CO2and S from arc volcanoes is fundamentally important to global climate, eruption forecasting, ore deposits, and the cycling of volatiles through subduction zones. However, all existing thermodynamic/empirical models have difficulties reproducing CO2‐H2O‐S trends observed in melt inclusions and provide widely conflicting results regarding the relationships between pressure and CO2/SO2in the vapor. In this study, we develop an open‐source degassing model, Sulfur_X, to track the evolution of S, CO2, H2O, and redox states in melt and vapor in ascending mafic‐intermediate magma. Sulfur_X describes sulfur degassing by parameterizing experimentally derived sulfur partition coefficients for two equilibria: RxnI. FeS (
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Abstract This study evaluates rates and pathways of methane (CH4) oxidation and uptake using14C‐based tracer experiments throughout the oxic and anoxic waters of ferruginous Lake Matano. Methane oxidation rates in Lake Matano are moderate (0.36 nmol L−1 day−1to 117 μmol L−1 day−1) compared to other lakes, but are sufficiently high to preclude strong CH4fluxes to the atmosphere. In addition to aerobic CH4oxidation, which takes place in Lake Matano's oxic mixolimnion, we also detected CH4oxidation in Lake Matano's anoxic ferruginous waters. Here, CH4oxidation proceeds in the apparent absence of oxygen (O2) and instead appears to be coupled to some as yet uncertain combination of nitrate (
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