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Geobiological Cycling of Gold: From Fundamental Process Understanding to Exploration Solutions
Centre for Tectonics, Resources and Exploration (TRaX), School of Earth and Environmental Sciences, the University of Adelaide, North Terrace, Adelaide, SA 5005, Australia
CSIRO Land and Water, Environmental Biogeochemistry, PMB2, Glen Osmond, SA 5064, Australia
Department of Mineralogy, South Australian Museum, Adelaide, SA 5000, Australia
Institute for Biology/Mikrobiology, Martin-Luther-University Halle-Wittenberg, DE-06120 Halle, Germany
School of Earth Sciences, the University of Queensland, Brisbane, QLD 4072, Australia
* Author to whom correspondence should be addressed.
Received: 7 September 2013; in revised form: 16 October 2013 / Accepted: 21 October 2013 / Published: 4 November 2013
Abstract: Microbial communities mediating gold cycling occur on gold grains from (sub)-tropical, (semi)-arid, temperate and subarctic environments. The majority of identified species comprising these biofilms are β-Proteobacteria. Some bacteria, e.g., Cupriavidus metallidurans, Delftia acidovorans and Salmonella typhimurium, have developed biochemical responses to deal with highly toxic gold complexes. These include gold specific sensing and efflux, co-utilization of resistance mechanisms for other metals, and excretion of gold-complex-reducing siderophores that ultimately catalyze the biomineralization of nano-particulate, spheroidal and/or bacteriomorphic gold. In turn, the toxicity of gold complexes fosters the development of specialized biofilms on gold grains, and hence the cycling of gold in surface environments. This was not reported on isoferroplatinum grains under most near-surface environments, due to the lower toxicity of mobile platinum complexes. The discovery of gold-specific microbial responses can now drive the development of geobiological exploration tools, e.g., gold bioindicators and biosensors. Bioindicators employ genetic markers from soils and groundwaters to provide information about gold mineralization processes, while biosensors will allow in-field analyses of gold concentrations in complex sampling media.
Keywords: gold; bacteria; cycling; biomineralization; review; exploration; bioindicator; biosensor
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Reith, F.; Brugger, J.; Zammit, C.M.; Nies, D.H.; Southam, G. Geobiological Cycling of Gold: From Fundamental Process Understanding to Exploration Solutions. Minerals 2013, 3, 367-394.
Reith F, Brugger J, Zammit CM, Nies DH, Southam G. Geobiological Cycling of Gold: From Fundamental Process Understanding to Exploration Solutions. Minerals. 2013; 3(4):367-394.
Reith, Frank; Brugger, Joël; Zammit, Carla M.; Nies, Dietrich H.; Southam, Gordon. 2013. "Geobiological Cycling of Gold: From Fundamental Process Understanding to Exploration Solutions." Minerals 3, no. 4: 367-394.