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Minerals 2018, 8(9), 401; https://doi.org/10.3390/min8090401

Reflecting on Gold Geomicrobiology Research: Thoughts and Considerations for Future Endeavors

1
School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005, Australia, Australia
2
CSIRO Land and Water, Contaminant Chemistry and Ecotoxicology, PMB2, Glen Osmond 5064, South Australia, Australia
*
Author to whom correspondence should be addressed.
Received: 13 August 2018 / Revised: 10 September 2018 / Accepted: 11 September 2018 / Published: 13 September 2018
(This article belongs to the Special Issue Geomicrobiology and Biogeochemistry of Precious Metals)
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Abstract

Research in gold (Au) geomicrobiology has developed extensively over the last ten years, as more Au-bearing materials from around the world point towards a consistent story: That microbes interact with Au. In weathering environments, Au is mobile, taking the form of oxidized, soluble complexes or reduced, elemental Au nanoparticles. The transition of Au between aqueous and solid states is attributed to varying geochemical conditions, catalyzed in part by the biosphere. Hence, a global Au-biogeochemical-cycle was proposed. The primary focus of this mini-review is to reflect upon the biogeochemical processes that contribute to what we currently know about Au cycling. In general, the global Au-biogeochemical-cycle begins with the liberation of gold-silver particles from a primary host rock, by physical weathering. Through oxidative-complexation, inorganic and organic soluble-Au complexes are produced. However, in the presence of microbes or other reductants—e.g., clays and Fe-oxides—these Au complexes can be destabilized. The reduction of soluble Au ultimately leads to the bioprecipitation and biomineralization of Au, the product of which can aggregate into larger structures, thereby completing the Au cycle. Evidence of these processes have been “recorded” in the preservation of secondary Au structures that have been observed on Au particles from around the world. These structures—i.e., nanometer-size to micrometer-size Au dissolution and reprecipitation features—are “snap shots” of biogeochemical influences on Au, during its journey in Earth-surface environments. Therefore, microbes can have a profound effect on the occurrence of Au in natural environments, given the nutrients necessary for microbial metabolism are sustained and Au is in the system. View Full-Text
Keywords: gold-biogeochemical-cycling; microorganisms; bacteria; biomineralization; gold nanoparticles; soluble gold; secondary gold; gold dissolution/reprecipitation; gold transport; gold kinetic mobility; gold particles; gold nuggets gold-biogeochemical-cycling; microorganisms; bacteria; biomineralization; gold nanoparticles; soluble gold; secondary gold; gold dissolution/reprecipitation; gold transport; gold kinetic mobility; gold particles; gold nuggets
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Shuster, J.; Reith, F. Reflecting on Gold Geomicrobiology Research: Thoughts and Considerations for Future Endeavors. Minerals 2018, 8, 401.

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