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Dominance of sulfur-fueled iron oxide reduction in low-sulfate freshwater sediments.
ISME J. 2015 Nov; 9(11):2400-12.IJ

Abstract

A central tenant in microbial biogeochemistry is that microbial metabolisms follow a predictable sequence of terminal electron acceptors based on the energetic yield for the reaction. It is thereby oftentimes assumed that microbial respiration of ferric iron outcompetes sulfate in all but high-sulfate systems, and thus sulfide has little influence on freshwater or terrestrial iron cycling. Observations of sulfate reduction in low-sulfate environments have been attributed to the presumed presence of highly crystalline iron oxides allowing sulfate reduction to be more energetically favored. Here we identified the iron-reducing processes under low-sulfate conditions within columns containing freshwater sediments amended with structurally diverse iron oxides and fermentation products that fuel anaerobic respiration. We show that despite low sulfate concentrations and regardless of iron oxide substrate (ferrihydrite, Al-ferrihydrite, goethite, hematite), sulfidization was a dominant pathway in iron reduction. This process was mediated by (re)cycling of sulfur upon reaction of sulfide and iron oxides to support continued sulfur-based respiration--a cryptic sulfur cycle involving generation and consumption of sulfur intermediates. Although canonical iron respiration was not observed in the sediments amended with the more crystalline iron oxides, iron respiration did become dominant in the presence of ferrihydrite once sulfate was consumed. Thus, despite more favorable energetics, ferrihydrite reduction did not precede sulfate reduction and instead an inverse redox zonation was observed. These findings indicate that sulfur (re)cycling is a dominant force in iron cycling even in low-sulfate systems and in a manner difficult to predict using the classical thermodynamic ladder.

Authors+Show Affiliations

Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA.School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA.School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA.Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA.Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA.No affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

25871933

Citation

Hansel, Colleen M., et al. "Dominance of Sulfur-fueled Iron Oxide Reduction in Low-sulfate Freshwater Sediments." The ISME Journal, vol. 9, no. 11, 2015, pp. 2400-12.
Hansel CM, Lentini CJ, Tang Y, et al. Dominance of sulfur-fueled iron oxide reduction in low-sulfate freshwater sediments. ISME J. 2015;9(11):2400-12.
Hansel, C. M., Lentini, C. J., Tang, Y., Johnston, D. T., Wankel, S. D., & Jardine, P. M. (2015). Dominance of sulfur-fueled iron oxide reduction in low-sulfate freshwater sediments. The ISME Journal, 9(11), 2400-12. https://doi.org/10.1038/ismej.2015.50
Hansel CM, et al. Dominance of Sulfur-fueled Iron Oxide Reduction in Low-sulfate Freshwater Sediments. ISME J. 2015;9(11):2400-12. PubMed PMID: 25871933.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Dominance of sulfur-fueled iron oxide reduction in low-sulfate freshwater sediments. AU - Hansel,Colleen M, AU - Lentini,Chris J, AU - Tang,Yuanzhi, AU - Johnston,David T, AU - Wankel,Scott D, AU - Jardine,Philip M, Y1 - 2015/04/14/ PY - 2014/08/18/received PY - 2015/02/24/revised PY - 2015/03/02/accepted PY - 2015/4/15/entrez PY - 2015/4/15/pubmed PY - 2016/6/24/medline SP - 2400 EP - 12 JF - The ISME journal JO - ISME J VL - 9 IS - 11 N2 - A central tenant in microbial biogeochemistry is that microbial metabolisms follow a predictable sequence of terminal electron acceptors based on the energetic yield for the reaction. It is thereby oftentimes assumed that microbial respiration of ferric iron outcompetes sulfate in all but high-sulfate systems, and thus sulfide has little influence on freshwater or terrestrial iron cycling. Observations of sulfate reduction in low-sulfate environments have been attributed to the presumed presence of highly crystalline iron oxides allowing sulfate reduction to be more energetically favored. Here we identified the iron-reducing processes under low-sulfate conditions within columns containing freshwater sediments amended with structurally diverse iron oxides and fermentation products that fuel anaerobic respiration. We show that despite low sulfate concentrations and regardless of iron oxide substrate (ferrihydrite, Al-ferrihydrite, goethite, hematite), sulfidization was a dominant pathway in iron reduction. This process was mediated by (re)cycling of sulfur upon reaction of sulfide and iron oxides to support continued sulfur-based respiration--a cryptic sulfur cycle involving generation and consumption of sulfur intermediates. Although canonical iron respiration was not observed in the sediments amended with the more crystalline iron oxides, iron respiration did become dominant in the presence of ferrihydrite once sulfate was consumed. Thus, despite more favorable energetics, ferrihydrite reduction did not precede sulfate reduction and instead an inverse redox zonation was observed. These findings indicate that sulfur (re)cycling is a dominant force in iron cycling even in low-sulfate systems and in a manner difficult to predict using the classical thermodynamic ladder. SN - 1751-7370 UR - https://www.unboundmedicine.com/medline/citation/25871933/Dominance_of_sulfur_fueled_iron_oxide_reduction_in_low_sulfate_freshwater_sediments_ L2 - https://doi.org/10.1038/ismej.2015.50 DB - PRIME DP - Unbound Medicine ER -