Bacterium helps formation of gold

Oct 07, 2009
This image shows maps of pure gold with other elements. By determining what elements there are, scientists can see where the gold is located in relation to the cells. These maps are quantitative X-ray fluorescence maps showing the distribution of gold, calcium, copper, iron, sulfur and zinc in an individual cell after a minute exposure to Au(III) at pH 7.0 (the quantified area is marked in the image, and concentrations are in the image). Credit: Reith et al, PNAS 5-9 October 2009.

Australian scientists have found that the bacterium Cupriavidus metallidurans catalyses the biomineralisation of gold by transforming toxic gold compounds to their metallic form using active cellular mechanism.

Researchers reported the presence of bacteria on gold surfaces but have never clearly elucidated their role. Now, an international team of scientists has found 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", explains Frank Reith, leader of the research and working at the University of Adelaide (Australia).

The experiments showed that C. metallidurans rapidly accumulates toxic gold complexes from a solution prepared in the lab. This process promotes gold toxicity, which pushes the to induce oxidative stress and metal resistance clusters as well as an as yet uncharacterized 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.

This is a transmission electron micrograph image of a C. metallidurans ultra-thin section containing a gold nanoparticle (in the middle). Credit: Reith et al, PNAS 5-9 October 2009.

For this study scientists combined synchrotron techniques at the European Synchrotron Radiation Facility (ESRF) and the Advanced Photon Source (APS) and molecular microbial techniques to understand the biomineralisation in bacteria. It is the first time that these techniques have been used in the same study, so Frank Reith brought together a multinational team of experts in both areas for the success of the experiment. The team was made up of scientists from the University of Adelaide, the Commonwealth Scientific and Research Organization (CSIRO), the University of California (US), the University of Western Ontario and the University of Saskatchewan (Canada), Martin-Luther-Universität (Germany), University of Nebraska-Lincoln (US), SCK.CEN (Belgium) and the APS (US) and the ESRF (France).

This is the first direct evidence that bacteria are actively involved in the cycling of rare and precious metals, such as gold. These results open the doors to the production of biosensors: "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 deposits. To achieve this we need to further characterize the gold-specific operon on a genomic as well as proteomic level. If funding for this research is granted I believe we can produce a functioning biosensor within three to five years", concludes Reith.

Source: European Synchrotron Radiation Facility

Explore further: Flexible metamaterial absorbers designed to suppress electromagnetic radiation

add to favorites email to friend print save as pdf

Related Stories

CSIRO scientist discovers natural 'invisible' gold

Jun 23, 2008

The search for these natural but 'invisible' nanoparticles is important. If they can be proved to exist, the knowledge will help give us a deeper understanding of how gold can be transported and deposited by geological processes, ...

Gold nuggets reveal their inner secrets

Oct 16, 2007

A study of the characteristics of gold nuggets from around Australia has overturned many years of accepted scientific wisdom on how nuggets form.

Changing gold

Feb 12, 2007

Gold is not as noble and stable as it has been previously thought. This is the conclusion of an international team of researchers from Germany, France and Sweden who came to the ESRF to study the structure of this material ...

The nanoworld of corrosion

Feb 09, 2006

The effect of corrosion has an impact on about 3% of the world's Gross Domestic Product. From a positive point of view, however, chemical attack of metal surfaces may result into surface nano-structures with ...

When gold becomes a catalyst

Jun 22, 2006

Gold has always been perceived as a precious material: you win a gold medal when you prove to be the best in a competition; you only get a Gold credit card when you are a preferential customer, and the jewelry ...

Recommended for you

Mapping the optimal route between two quantum states

18 hours ago

As a quantum state collapses from a quantum superposition to a classical state or a different superposition, it will follow a path known as a quantum trajectory. For each start and end state there is an optimal ...

Spin-based electronics: New material successfully tested

23 hours ago

Spintronics is an emerging field of electronics, where devices work by manipulating the spin of electrons rather than the current generated by their motion. This field can offer significant advantages to computer technology. ...

Verifying the future of quantum computing

Jul 30, 2014

Physicists are one step closer to proving the reliability of a quantum computer – a machine which promises to revolutionise the way we trade over the internet and provide new tools to perform powerful simulations.

User comments : 0