Promotion and nucleation of carbonate precipitation during microbial iron reduction

Abstract

Iron-bearing early diagenetic carbonate cements are common in sedimentary rocks, where they are thought to be associated with microbial iron reduction. However, little is yet known about how local environments around actively iron-reducing cells affect carbonate mineral precipitation rates and compositions. Precipitation experiments with the iron-reducing bacterium Shewanella oneidensis MR-1 were conducted to examine the potential role of cells in promoting precipitation and to explore the possible range of precipitate compositions generated in varying fluid compositions. Actively iron-reducing cells induced increased carbonate mineral saturation and nucleated precipitation on their poles. However, precipitation only occurred when calcium was present in solution, suggesting that cell surfaces lowered local ferrous iron concentrations by adsorption or intracellular iron oxide precipitation even as they locally raised pH. Resultant precipitates were a range of thermodynamically unstable calcium-rich siderites that would likely act as precursors to siderite, calcite, or even dolomite in nature. By modifying local pH, providing nucleation sites, and altering metal ion concentrations around cell surfaces, iron-reducing micro-organisms could produce a wide range of carbonate cements in natural sediments.

Interaction between lithification and resource availability in the microbialites of Río Mesquites, Cuatro Ciénegas, México

“…Calcification in the oncoid microbialites of R ıo Mesquites is thought to be photosynthetically driven (Garcia-Pichel et al, 2004;Elser et al, 2005), but CaCO 3 deposition can also be promoted by anaerobic heterotrophic metabolisms, such as dissimilatory iron reduction or sulphate reduction (Visscher & Stolz, 2005;Zeng & Tice, 2014). When photosynthesis is the main driver of calcification, environmental conditions that increase the rate of photosynthesis also increase the rate of calcification, as shown in Elser et al (2005) and Garcia-Pichel et al (2004).…”

Remineralization of ferrous carbonate from bioreduction of natural goethite in the Lorraine iron ore (Minette) by Shewanella putrefaciens

“…These are for example -the nature and relative concentration of ions in the medium, the cell density and/or organic polymers, the nature of the Fe(III) species and electron donor Zachara et al, 2002;Zegeye et al, 2005;O'Loughlin et al, 2010;Sergent et al, 2011;Jorand et al, 2013;Zeng and Tice, 2014). Indeed, regarding the low phosphate concentrations (~7 μM), no vivianite could have significantly precipitated.…”

“…Sulphate (~9 mM) and alkaline pH were reported to inhibit magnetite formation (Zachara et al, 2002;Behrends and Van Cappellen, 2007) and, on the contrary, the high cell concentrations and alkaline pH would promote siderite formation , Zachara et al, 2002, which is the case in our experiments. Liu et al (2001) Roh et al, 2003;Zeng and Tice, 2014), disk-like shape or flake (Roh et al, 2003) or pseudorhombohedral shape in the presence of a relatively large amount of carbonate (30 mM) or Ca 2+ (10 mM). In the SMW, where salt concentrations of Ca 2+ and CO 3 2− were much more lower (e.g.…”

The microbially driven formation of siderite in salt marsh sediments

“…The formation of siderite is often assumed to involve microbially mediated chemical reactions, such as bacterial iron reduction, that produce dissolved iron and generate alkalinity through the oxidation of organic carbon (Baumann, Birgel, Wargreich, & Peckmann, 2016;Van Lith et al, 2003;Roberts et al, 2013;Sel, Radha, Dideriksen, & Navrotsky, 2012). However, bacterial iron reduction alone tends to push the pH of the pore fluid higher than 7.2 (Soetaert, Hofmann, Middleberg, Meysman, & Greenwood, 2007;Zeng & Tice, 2014), which means that for siderite to form, more is needed than simply local conditions that favor bacterial iron reduction.…”