‘Bio-mining’ microbe’s secrets revealed

[SANTIAGO] Scientists in Chile have described for the first time the molecular machinery of a bacterium used to extract copper and other metals from low-grade mineral concentrates in a process called bio-mining.

The findings were announced at the 12th International Biotechnology Symposium, held in Santiago last month.

“Understanding the bacterium is crucial for mining countries like Chile, where high-grade copper reserves are no longer available,” lead investigator David Holmes, of Andres Bello University, Chile, told SciDev.Net.

In low-grade ores, copper is bound in a matrix containing sulphur. A bacterium called Acidithiobacillus ferrooxidans can breaks the bonds between copper and sulphur to obtain energy. This results in the metal’s release.

Understanding the microbe’s biochemistry could lead to improvements to current bio-mining procedures. But experimental investigation of the microbe’s metabolism using standard genetic techniques has proven difficult, despite considerable effort invested in many laboratories around the world, says Holmes.

To overcome this limitation, Holmes’s team and colleagues at the Millennium Institute of Fundamental and Applied Biology used bioinformatics – analysis of biological information using computers and statistical techniques.

The researchers analysed two publicly available sequences of the bacterium’s DNA. Using this information, they identified the molecular processes enabling the microbe to acquire energy from ores, and confirmed their findings in laboratory experiments.

Based on their findings, the researchers were able to improve the capacity of A. ferrooxidans to form thin layers called ‘bio-films’ made up of many individual bacteria. It is by forming these films that the microbe can extract copper from surfaces it coats. A new method of copper extraction is being patented as a result of this research.

“This is a nice example of a theoretical research that will allow new applications in production processes,” says Holmes.

“From a ‘pure science’ perspective, we are intrigued by the strange metabolism of A. ferrooxidans, which gives us a glimpse of the first micro-organisms that lived on the planet, allowing us to address fundamental questions about life on Earth. And from an applied point of view, the bacterium is very important for the future of mining.”

Commercial use of microbes such as A. ferrooxidans for metal extraction is widespread. The approach is less expensive and has fewer environmental impacts than conventional processes.