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In this work, a gold biosensor has been constructed and characterised in Escherichia coli (E. coli). Though gold biosensors have been previously reported, a NOT gate gold biosensing genetic circuit was constructed using an orthogonal inverter system as an alternative to a circuit where output is contingent solely on input. This enables the detection of changes in gold concentration whereby circuit remains OFF in presence of inducer and ON in absence of inducer. The proposed biosensor is an alternative to conventional forms of gold detection such as Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The constructed biosensor is a collection of components – golTSB operon (isolated from Salmonella enterica), mf-Lon protease (isolated from Mesoplasma florum) and associated ssrA degradation tag with GFP acting as a reporter. The minimum time and concentration required by the biosensor gol-mflon-GFP (GMG) to achieve the ON output is characterised here using plate reader data derived from a single multi-stage assay.

The prospects for extracting finely dispersed gold and other useful components from the magnetic tailings of gold recovery plants and other sources are shown. This is achieved by using the process of leaching these particles and their extraction by sorption on metastable nanocrystalline water structures. A gold simulator, a colloid of molecular copper, is passed through the sorbent of a metastable nanocrystalline water structure. After three passes through the sorbent, the copper appears to be completely sorbed. Thus, according to the qualitative analysis of copper sorption, the possibility of extracting gold using this technology is confirmed. [ABSTRACT FROM AUTHOR]

Abstract: Economic concentrations of detrital gold are rare in young foreland basins due to paucity of significant gold sources, and a paucity of sediment recycling processes during filling of the foreland basin. Gold shed into the foreland basins is typically widely dispersed in an overwhelming volume of immature basin-fill detritus of no economic significance. In the actively forming Canterbury Basin of New Zealand, minor gold concentration occurs at the mountain front in the bed of the Rakaia River, and 60 km downstream on beaches and the crest of foredunes at the river mouth. The Cretaceous–Tertiary Denver and Western Canada Basins in North America also have minor gold concentrations at the mountain front, and minor gold dispersal into the basin. Tectonic quiescence in the middle Tertiary in the Denver Basin kept gold within 20 km of the mountain front, where renewed uplift in late Tertiary caused minor economic concentrations to form in modern streams. Gold has been transported ca. 200 km across the Western Canada basin by progressive recycling of gravel during slow (ca. 10 to 50 m/Ma) middle Tertiary–Recent regional uplift and tilting, but little concentration has occurred. Development of significant placers in a foreland basin, the generally accepted setting for the Witwatersrand Au-U palaeoplacers, appears to require specific tectonic conditions during and/or after basin evolution to drive the sedimentary recycling necessary for significant placer development. Such tectonic conditions have not occurred in an any of the three young foreland basins examined in this study. [Copyright &y& Elsevier]