title: Fate of Cd during microbial Fe(III) mineral reduction by a novel and Cd-tolerant Geobacter species.
abstract: Fe(III) (oxyhydr)oxides affect the mobility of contaminants in the environment by providing reactive surfaces for sorption. This includes the toxic metal cadmium (Cd), which prevails in agricultural soils and is taken up by crops. Fe(III)-reducing bacteria can mobilize such contaminants by Fe(III) mineral dissolution or immobilize them by sorption to or coprecipitation with secondary Fe minerals. To date, not much is known about the fate of Fe(III) mineral-associated Cd during microbial Fe(III) reduction. Here, we describe the isolation of a new Geobacter sp. strain Cd1 from a Cd-contaminated field site, where the strain accounts for 10(4) cells g(-1) dry soil. Strain Cd1 reduces the poorly crystalline Fe(III) oxyhydroxide ferrihydrite in the presence of at least up to 112 mg Cd L(-1). During initial microbial reduction of Cd-loaded ferrihydrite, sorbed Cd was mobilized. However, during continuous microbial Fe(III) reduction, Cd was immobilized by sorption to and/or coprecipitation within newly formed secondary minerals that contained Ca, Fe, and carbonate, implying the formation of an otavite-siderite-calcite (CdCO3-FeCO3-CaCO3) mixed mineral phase. Our data shows that microbially mediated turnover of Fe minerals affects the mobility of Cd in soils, potentially altering the dynamics of Cd uptake into food or phyto-remediating plants.
authors.affiliation: Geomicrobiology, Center for Applied Geosciences, University of Tuebingen , 72076 Tuebingen, Germany.
authors.forename: E Marie
authors.initials: EM
authors.lastname: Muehe
authors.forename: Martin
authors.initials: M
authors.lastname: Obst
authors.forename: Adam
authors.initials: A
authors.lastname: Hitchcock
authors.forename: Tolek
authors.initials: T
authors.lastname: Tyliszczak
authors.forename: Sebastian
authors.initials: S
authors.lastname: Behrens
authors.forename: Christian
authors.initials: C
authors.lastname: Schröder
authors.forename: James M
authors.initials: JM
authors.lastname: Byrne
authors.forename: F Marc
authors.initials: FM
authors.lastname: Michel
authors.forename: Ute
authors.initials: U
authors.lastname: Krämer
authors.forename: Andreas
authors.initials: A
authors.lastname: Kappler
mesh_terms: D000222:Adaptation, Physiological / Q000187:drug effects*; D001673:Biodegradation, Environmental / Q000187:drug effects; D002104:Cadmium / Q000378:metabolism* / Q000633:toxicity*; D002254:Carbonates / Q000378:metabolism; D005290:Ferric Compounds / Q000378:metabolism; D045302:Geobacter / Q000187:drug effects / Q000378:metabolism*; D005858:Germany; D007501:Iron / Q000378:metabolism*; D008903:Minerals / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012989:Soil Pollutants / Q000032:analysis; D013052:Spectrometry, X-Ray Emission
chemical_list: D002254:Carbonates; D005290:Ferric Compounds; D008903:Minerals; D012336:RNA, Ribosomal, 16S; D012989:Soil Pollutants; D002104:Cadmium; C092844:ferric oxyhydroxide; D007501:Iron; C486982:siderite