JOIN USAn international team has found that the bacterium Cupriavidus metallidurans catalyses the biomineralisation of gold by transforming toxic gold compounds to their metallic form using active cellular mechanism.
According to the scientists, they have found evidence indicating that there may be a biological reason for the presence of these bacteria on gold grain surfaces.
"A number of years ago we discovered that the metal-resistant bacterium Cupriavidus metallidurans occurred on gold grains from two sites in Australia. The sites are 3500 km apart, in southern New South Wales and northern Queensland, so when we found the same organism on grains from both sites we thought we were onto something.
"It made us wonder why these organisms live in this particular environment. The results of this study point to their involvement in the active detoxification of gold complexes leading to formation of gold biominerals," team leader Frank Reith of the University of Adelaide said.
The experiments showed that 'C. metallidurans' rapidly accumulates toxic gold complexes from a solution prepared in the laboratory. This process promotes gold toxicity, pushing the bacterium to induce oxidative stress and metal resistance clusters as well as an as yet uncharacterised gold-specific gene cluster in order to defend its cellular integrity.
This leads to active biochemically-mediated reduction of gold complexes to nano-particulate, metallic gold, which may contribute to the growth of gold nuggets, the team said.
For this study, the scientists combined synchrotron techniques at the European Synchrotron Radiation Facility and the Advanced Photon Source (APS) and molecular microbial techniques to understand the biomineralisation in bacteria.
"The discovery of an Au-specific operon means that we can now start to develop gold-specific biosensors, which will help mineral explorers to find new gold deposits. To achieve this we need to further characterise the gold-specific operon on a genomic as well as proteomic level," Reith said.