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Sulfur-mediated electron shuttling during bacterial iron reduction.

Sulfur-mediated electron shuttling during bacterial iron reduction.

Science (New York, N.Y.) (2014-05-03)

Theodore M Flynn, Edward J O'Loughlin, Bhoopesh Mishra, Thomas J DiChristina, Kenneth M Kemner

ABSTRACT

Microbial reduction of ferric iron [Fe(III)] is an important biogeochemical process in anoxic aquifers. Depending on groundwater pH, dissimilatory metal-reducing bacteria can also respire alternative electron acceptors to survive, including elemental sulfur (S(0)). To understand the interplay of Fe/S cycling under alkaline conditions, we combined thermodynamic geochemical modeling with bioreactor experiments using Shewanella oneidensis MR-1. Under these conditions, S. oneidensis can enzymatically reduce S(0) but not goethite (α-FeOOH). The HS(-) produced subsequently reduces goethite abiotically. Because of the prevalence of alkaline conditions in many aquifers, Fe(III) reduction may thus proceed via S(0)-mediated electron-shuttling pathways.

MATERIALS

Product Number

Brand

Product Description

Sigma-Aldrich

Carbonyl iron, ≥97% Fe basis

Sigma-Aldrich

Iron, ≥99%, reduced, powder (fine)

Supelco

Sulfur, PESTANAL^®, analytical standard

Sigma-Aldrich

Iron, granular, 10-40 mesh, >99.99% trace metals basis

Sigma-Aldrich

Iron, foil, thickness 0.25 mm, ≥99.99% trace metals basis

Sigma-Aldrich

Iron, wire, diam. 1.0 mm, ≥99.9% trace metals basis

Sigma-Aldrich

Sulfur, flakes, ≥99.99% trace metals basis

Sigma-Aldrich

Sulfur, 99.998% trace metals basis

Sigma-Aldrich

Sulfur, powder, 99.98% trace metals basis

Iron, foil, light tested, 25x25mm, thickness 0.01mm, 99.85%

Iron, microfoil, disks, 10mm, thinness 0.15μm, specific density 176.7μg/cm², permanent mylar 3.5μm support, 99.99+%

Iron, rod, 100mm, diameter 19mm, as drawn, soft ingot 99.8%

Iron, rod, 1000mm, diameter 19mm, as drawn, soft ingot 99.8%

Iron, foil, 8mm disks, thickness 0.038mm, hard, 99.5%

Iron, foil, not light tested, 25x25mm, thickness 0.001mm, 99.85%

Iron, foil, not light tested, 100x100mm, thickness 0.004mm, 99.85%

Iron, foil, light tested, 25x25mm, thickness 0.075mm, as rolled, 99.99+%

Iron, foil, light tested, 100x100mm, thickness 0.05mm, hard, 99.5%

Iron, foil, 8mm disks, thickness 0.125mm, as rolled, 99.99+%

Iron, rod, 1000mm, diameter 9.5mm, as drawn, soft ingot 99.8+%

Iron, foil, 8mm disks, thickness 0.9mm, as rolled, 99.5%

Iron, foil, 25x25mm, thickness 0.125mm, hard, 99.5%

Iron, foil, not light tested, 25x25mm, thickness 0.005mm, 99.85%

Iron, rod, 200mm, diameter 6.35mm, as drawn, soft ingot 99.8%

Iron, rod, 150mm, diameter 6.0mm, as drawn, 99.99+%

Iron, rod, 100mm, diameter 12.7mm, as drawn, 98+%

Iron, foil, 100x100mm, thickness 1.0mm, as rolled, 99.5%

Iron, foil, 5m coil, thickness 0.038mm, hard, 99.5%

Iron, foil, 6mm disks, thickness 0.003mm, 99.85%

Iron, foil, 50mm disks, thickness 0.15mm, hard, 99.5%