Biogeochemical and Environmental Factors in Fe Biomineralization: Magnetite and Siderite Formation

Abstract

The formation of siderite and magnetite by Fe(III)-reducing bacteria may play an important role in C and Fe geochemistry in subsurface and ocean sediments. The objective of this study was to identify environmental factors that control the formation of siderite (FeCO3) and magnetite (Fe3O4) by Fe(III)-reducing bacteria. Psychrotolerant (<20°C), mesophilic (20–35°C) and thermophilic (>45°C) Fe(III)-reducing bacteria were used to examine the reduction of a poorly crystalline iron oxide, akaganeite (β-FeOOH), without a soluble electron shuttle, anthraquinone disulfuonate (AQDS), in the presence of N2, N2-CO2(80:20, V:V), H2 and H2-CO2 (80:20, V:V) headspace gases as well as in -buffered medium (30–210 mM) under a N2 atmosphere. Iron biomineralization was also examined under different growth conditions such as salinity, pH, incubation time, incubation temperature and electron donors. Magnetite formation was dominant under a N2 and a H2 atmosphere. Siderite formation was dominant under a H2-CO2 atmosphere. A mixture of magnetite and siderite was formed in the presence of a N2-CO2 headspace. Akaganeite was reduced and transformed to siderite and magnetite in a -buffered medium (>120 mM) with lactate as an electron donor in the presence of a N2 atmosphere. Biogeochemical and environmental factors controlling the phases of the secondary mineral suite include medium pH, salinity, electron donors, atmospheric composition and incubation time. These results indicate that microbial Fe(III) reduction may play an important role in Fe and C biogeochemistry as well as C sequestration in natural environments.

Formation of tabular single-domain magnetite induced by Geobacter metallireducens GS-15

“…High partial pressures of CO 2 appear to preferentially favor goethite formation instead of lepidocrocite (14), as is also evident in our experiment. The Eh-pH (Ϫ4 mV Ϫ 7.28) data obtained from our experiment, however, does not fit into the stability field of lepidocrocite in the conventional Eh-pH (100 -300 mV 3 7) stability diagram (8,26). This discrepancy may be explained by the biogenic origin of lepidocrocite that is mediated by the metabolic activity of GS-15.…”

“…The formation of prismatic magnetite crystals has not been reported by any other mechanism at low temperature (Ͻ100°C). Extracellular biogenic magnetite is formed by several types of bacteria (7,8), but is typically poorly crystalline and close to diamond and other equilibrium shapes such as cubes, octahedrons, and dodecahedrons.…”

Products of abiotic U(VI) reduction by biogenic magnetite and vivianite

“…The biostimulation of DMRB will likely lead to biological Fe(III) reduction (Wielinga et al, 2000;Finneran et al, 2002;Anderson et al, 2003;Elias et al, 2004;) and production of sorbed Fe(II) or Fe(II)-bearing minerals as metabolic products. The Fe(II)-bearing phases found include magnetite, siderite, vivianite, ferruginous smectite, and green rust (Bell et al, 1987;Roden and Zachara, 1996;Fredrickson et al, 1998;Zachara et al, 1998;Dong et al, 2000;Roh et al, 2003;O'Loughlin et al, 2007;Komlos et al, 2008;O'Loughlin et al, 2010). Sorbed Fe(II) and the Fe(II)-bearing biogenic phases can provide a reservoir of reducing capacity where reduction of U(VI) may occur due to abiotic interactions .…”

Metal Reduction and Iron Biomineralization by a Psychrotolerant Fe(III)-Reducing Bacterium, Shewanella sp. Strain PV-4

“…Dissimilatory metal reduction is proposed to be an early form of microbial respiration (16). Reduction of metals by bacteria is generally coupled with the oxidation of organic matter (16,28,29). Therefore, the ability to reduce metals can be exploited not only for the bioreduction or immobilization of many toxic metals, including cobalt, chromium, uranium, and technetium, but also for the biotransformation of organic contaminants to benign products such as carbon dioxide (7).…”