Biotransformation of two-line silica-ferrihydrite by a dissimilatory Fe(III)-reducing bacterium: formation of carbonate green rust in the presence of phosphate

Abstract

Abstract-The reductive biotransformation of two Si-ferrihydrite coprecipitates (1 and 5 mole % Si) by Shewanella putrefaciens, strain CN32, was investigated in 1,4-piperazinediethanesulfonic acid-buffered media (pH ϳ7) with lactate as the electron donor. Anthraquinone-2,6-disulfonate, an electron shuttle, was present in the media. Experiments were performed without and with PO 4 3Ϫ (P) (1 to 20 mmol/L) in media containing 50 mmol/L Fe. Our objectives were to define the combined effects of SiO 4 4Ϫ (Si) and P on the bioreducibility and biomineralization of ferrihydrites under anoxic conditions. Iron reduction was measured as a function of time, solids were characterized by powder X-ray diffraction and Mössbauer spectroscopy, and aqueous solutions were analyzed for Si, P, Cl Ϫ and inorganic carbon. Both of the ferrihydrites were rapidly reduced regardless of the Si and P content. Si concentration had no effect on the reduction rate or mineralization products. Magnetite was formed in the absence of P whereas carbonate green rust GR( ) varied with P concentration; the ratio was 2 in 1 mmol/L P and approached 1 with 4-and 10 mmol/L P. Green rust appeared to form by solid-state transformation of ferrihydrite. Media P and Si concentration dictated the mechanism of transformation. In the 1 mole % Si coprecipitate with 1 mmol/L P, an intermediate Fe(II)/Fe(III) phase with structural Fe(II) slowly transformed to GR with time. In contrast, when ferrihydrite contained more Si (5 mole %) and/or contained higher P (4 mmol/L), sorbed Fe(II) and residual ferrihydrite together transformed to GR. Despite similar chemistries, P was shown to have a profound effect on extent of ferrihydrite reduction and biotransformations while that of Si was minimal.

The mineralogic transformation of ferrihydrite induced by heterogeneous reaction with bioreduced anthraquinone disulfonate (AQDS) and the role of phosphate

“…When AQDS is used as a ETM with MRB, an electron donor, and ferrihydrite/or lepidocrocite, it is generally present at lower concentration with a Fe(II) equiv /Fe(III) ratio ranging from approximately 0.0004 (Zegeye et al, 2007;Coker et al, 2008) to 0.0072 Kukkadapu et al, 2004). Consequently, the heterogeneous reductant (AH 2 DS) is supplied at a low, but more sustained and uniform concentration than in the present experiments as a result of bacterial respiration.…”

“…The Fe(II) spectral area was higher than the maximum amount of vivianite (3%) that could form, given the P/(Fe + P) ratio of 2% used in the experiment (Table 1). The derived Fe(II) Mö ssbauer parameters were also different from those of vivianite (e.g., Kukkadapu et al, 2004;Murad and Cashion 2004). The Fe(II) and ferrihydrite phases magnetically ordered at 10 K (Fig.…”

“…The following bioavailability sequence has been observed based on total Fe(III) mass: ferrihydrite $ lepidocrocite > nanocrystalline Fe(III) oxides > Fe(III) containing phyllosilicates (smectite, nontronite, illite) > crystalline Fe(III) oxides (Roden and Zachara, 1996;Kostka et al, 2002;Zachara et al, 2002;Bonneville et al, 2004). The bioreduction of ferrihydrite and lepidocrocite, specifically, can lead to major changes in mineralogy Hansel et al, 2003;Kukkadapu et al, 2004Kukkadapu et al, , 2005O'Loughlin et al, 2007).…”

“…Reductive mineral phases have been observed in AQDS-containing Fe(III) oxide systems, such as green rust and ferrous hydroxy carbonate (Ona-Nguema et al, 2002;Kukkadapu et al, 2004Kukkadapu et al, , 2005O'Loughlin et al, 2007;O'Loughlin, 2008), that are infrequently observed in its absence. These mineral forms are considered biomineralization products, but are they?…”

Electrically conductive bacterial nanowires produced by Shewanella oneidensis strain MR-1 and other microorganisms

“…Wild-type MR-1, GSPD, and ⌬MTRC͞OMCA were grown in chemostat cultures using a chemically defined medium containing 18 mM lactate as the growthlimiting nutrient and O 2 at a dissolved concentration of Ϸ2% of air saturation. Samples taken at steady state were used to inoculate anaerobic defined medium containing 20 mM silica-substituted ferrihydrite (29) as the sole terminal electron acceptor and 20 mM lactate as the electron donor. Cultures were incubated at 30°C and 25 rpm and sampled for Fe(II) by adding 0.5 ml to 0.5 ml of 1 M HCl with a needle and 1-ml syringe in an anaerobic glovebag.…”