Abstract
The tungsten–microbial interactions and microbial bioprocessing of tungsten ores, which are still underexplored, are the focus of the current study. Here we show that the biotransformation of tungsten mineral scheelite performed by the extreme thermoacidophile Metallosphaera sedula leads to the breakage of scheelite structure and subsequent tungsten solubilization. Total soluble tungsten is significantly higher in cultures containing M. sedula grown on scheelite than the abiotic control, indicating active bioleaching. Advanced analytical electron microscopy was used in order to achieve nanoscale resolution ultrastructural studies of M. sedula grown on tungsten bearing scheelite. In particular, we describe that M. sedula mediated the biotransformation of scheelite, which was accompanied by the release of tungsten into solution and tungsten biomineralization of the cell surface. Furthermore, we observed intracellular incorporation of redox heterogenous Mn- and Fe-containing nano-clusters. Our results highlight unique metallophilic life in hostile environments extending the knowledge of tungsten biogeochemistry. Based on these findings biohydrometallurgical processing of tungsten ores can be further explored. Importantly, biogenic tungsten carbide-like nanolayers described herein are potential targets for developing nanomaterial biotechnology.
Highlights
A great variety of evolutionally diversified metallophilic microorganisms are equipped with unique capabilities and fascinating metabolic routes for manipulating minerals and dissolving them to access useful metals
Metallosphaera sedula was aerobically cultivated on a calcium tungstate mineral scheelite at 73◦C with CO2 supplementation (Figure 1A, Supplementary Figure S1, and Supplementary Video S1)
It is possible to propose that the M. sedula mediated biooxidation of iron and manganese destroyed the scheelite structure, leading to the release of W into solution
Summary
A great variety of evolutionally diversified metallophilic microorganisms are equipped with unique capabilities and fascinating metabolic routes for manipulating minerals and dissolving them to access useful metals. Tungsten (W) is the only metal from the third transition series, which is shown to occur in biomolecules, where it is used. Tungsten Encrustation of Metallosphaera sedula in a few species of bacteria and methanogenic and hyperthermophilic archaea as an essential element, constitutive, and functional part of tungstopterin cofactor (Chan et al, 1995; Kletzin, 1996; Andreesen and Makdessi, 2008). Microbial assimilation of tungsten has been proposed in hydrothermal environments, where high concentrations of tungsten might be connected with metabolic activity of hyperthermophilic archaea (Holden and Adams, 2003). The recently shown passive tungstate biosorption by living or inactivated microbial cells has been suggested as an efficient strategy for tungsten recovery and recycling from aquatic systems (Malekzadeh et al, 2007; Takashi et al, 2013, 2016; Ogi et al, 2016). The currently used hydrometallurgical or pyrometallurgical processes enable the breakage of the tungsten–oxygen bond and release of the associated tungsten; the bioprocessing of tungsten bearing materials is not yet established
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