title: Ligand-enhanced abiotic iron oxidation and the effects of chemical versus biological iron cycling in anoxic environments.
abstract: This study introduces a newly isolated, genetically tractable bacterium ( Pseudogulbenkiania sp. strain MAI-1) and explores the extent to which its nitrate-dependent iron-oxidation activity is directly biologically catalyzed. Specifically, we focused on the role of iron chelating ligands in promoting chemical oxidation of Fe(II) by nitrite under anoxic conditions. Strong organic ligands such as nitrilotriacetate and citrate can substantially enhance chemical oxidation of Fe(II) by nitrite at circumneutral pH. We show that strain MAI-1 exhibits unambiguous biological Fe(II) oxidation despite a significant contribution (∼30-35%) from ligand-enhanced chemical oxidation. Our work with the model denitrifying strain Paracoccus denitrificans further shows that ligand-enhanced chemical oxidation of Fe(II) by microbially produced nitrite can be an important general side effect of biological denitrification. Our assessment of reaction rates derived from literature reports of anaerobic Fe(II) oxidation, both chemical and biological, highlights the potential competition and likely co-occurrence of chemical Fe(II) oxidation (mediated by microbial production of nitrite) and truly biological Fe(II) oxidation.
authors: Division of Geologial and Planetary Sciences, California Institute of Technology, Pasadena, California, USA.
authors: Sebastian H
authors: SH
authors: Kopf
authors: Cynthia
authors: C
authors: Henny
authors: Dianne K
authors: DK
authors: Newman
mesh_terms: D002614:Chelating Agents / Q000378:metabolism; D058440:Denitrification; D005296:Ferrous Compounds / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D008024:Ligands; D009346:Neisseriaceae / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism*; D010084:Oxidation-Reduction; D010231:Paracoccus denitrificans / Q000378:metabolism
chemical_list: D002614:Chelating Agents; D005296:Ferrous Compounds; D008024:Ligands; D009566:Nitrates; D007501:Iron
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