TY - JOUR

T1 - Microbial reduction of ferrihydrite-organic matter coprecipitates by Shewanella putrefaciens and Geobacter metallireducens in comparison to mediated electrochemical reduction

AU - Poggenburg, Christine

AU - Mikutta, Robert

AU - Sander, Michael

AU - Schippers, Axel

AU - Marchanka, Alexander

AU - Dohrmann, Reiner

AU - Guggenberger, Georg

PY - 2016/12/30

Y1 - 2016/12/30

N2 - Despite numerous studies seeking to elucidate the effect of various specific organic compounds on the reactivity and stability of Fe oxyhydroxides in soil, studies examining the effect of natural organic matter (NOM) on the microbial reduction of Fe-organic matter (OM) coprecipitates are still rare. In this study, pure ferrihydrite (Fh) and Fe-OM coprecipitates were synthesized using three different types of NOM (extracellular polymeric substances extracted from Bacillus subtilis, OM extracted from the Oi horizon of a Cambisol, and OM extracted from the Oa horizon of a Podzol). These phases were characterized by N2 gas adsorption, nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), NOM desorption experiments, and mediated electrochemical reduction (MER). Iron(III) reduction under anaerobic conditions was monitored for 16 days using two different strains of dissimilatory Fe(III)-reducing bacteria (Shewanella putrefaciens, Geobacter metallireducens). Mineral transformation during reduction was determined by XRD and FTIR of the solid post-incubation phases. Fe(III) reduction by Shewanella putrefaciens was influenced by the amount of available electron shuttling molecules provided by the NOM, whereas the Fe(III) reduction by Geobacter metallireducens as well as abiotic Fe(III) reduction was influenced by particle size and NOM-induced aggregation. The specific surface area proved to be a poor predictor of Fe reduction of Fe-OM coprecipitates. This study emphasizes that certain physicochemical properties of natural Fe oxyhydroxides (composition of sorbed NOM and aggregation state) impact the Fe reduction by distinct microorganisms to differing degrees. Understanding environmental Fe and C cycling, therefore, requires experimental approaches extending beyond the use of pure Fe oxyhydroxides and model organisms.

AB - Despite numerous studies seeking to elucidate the effect of various specific organic compounds on the reactivity and stability of Fe oxyhydroxides in soil, studies examining the effect of natural organic matter (NOM) on the microbial reduction of Fe-organic matter (OM) coprecipitates are still rare. In this study, pure ferrihydrite (Fh) and Fe-OM coprecipitates were synthesized using three different types of NOM (extracellular polymeric substances extracted from Bacillus subtilis, OM extracted from the Oi horizon of a Cambisol, and OM extracted from the Oa horizon of a Podzol). These phases were characterized by N2 gas adsorption, nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), NOM desorption experiments, and mediated electrochemical reduction (MER). Iron(III) reduction under anaerobic conditions was monitored for 16 days using two different strains of dissimilatory Fe(III)-reducing bacteria (Shewanella putrefaciens, Geobacter metallireducens). Mineral transformation during reduction was determined by XRD and FTIR of the solid post-incubation phases. Fe(III) reduction by Shewanella putrefaciens was influenced by the amount of available electron shuttling molecules provided by the NOM, whereas the Fe(III) reduction by Geobacter metallireducens as well as abiotic Fe(III) reduction was influenced by particle size and NOM-induced aggregation. The specific surface area proved to be a poor predictor of Fe reduction of Fe-OM coprecipitates. This study emphasizes that certain physicochemical properties of natural Fe oxyhydroxides (composition of sorbed NOM and aggregation state) impact the Fe reduction by distinct microorganisms to differing degrees. Understanding environmental Fe and C cycling, therefore, requires experimental approaches extending beyond the use of pure Fe oxyhydroxides and model organisms.

KW - Extracellular polymeric substances

KW - Geobacter metallireducens

KW - Iron oxyhydroxides

KW - Mediated electrochemical reduction

KW - Natural organic matter

KW - Shewanella putrefaciens

UR - http://www.scopus.com/inward/record.url?scp=84999851954&partnerID=8YFLogxK

U2 - 10.1016/j.chemgeo.2016.09.031

DO - 10.1016/j.chemgeo.2016.09.031

M3 - Article

AN - SCOPUS:84999851954

VL - 447

SP - 133

EP - 147

JO - Chemical geology

JF - Chemical geology

SN - 0009-2541

ER -