Turning dirt into gold has been the stuff of myth and legend for ages. The cautionary tale of king Midas is a testament to mankind's love of gold and alchemists have been trying to turn all sorts of metals into gold for centuries. Eventually US credit rating agencies managed to work out a foolproof way of turning rubbish into gold by slapping AAA ratings on toxic mortgage-based securities, but we digress.
Researchers have now uncovered the real deal. Delftia acidovorans lives in sticky biofilms that form on top of gold deposits, but exposure to dissolved gold ions can kill it. To protect itself the bacterium has evolved a chemichal that detoxifies gold ions and turns them into harmless gold nanoparticles. The nanoparticles harmlessly accumulate outside the bacterial cells.
The discovery is not purely academic, as it could be used on an industrial scale. Nathan Magarvey of McMaster University in Ontario led the team that discovered the bacteria's unique trick.
"This could have potential for gold extraction," Magarvey told the New Scientist. "You could use the bug, or the molecules they secrete."
Magarvey believes the bacteria could be used to dissolve gold out of water, or to design sensors that would identify gold rich streams and rivers. The chemical used by the bug is a protein dubbed delftibactin A. It transforms gold ions into particles of gold 25 to 50 nanometers across and the particles accumulate wherever the bacteria grow.
However, the gold nanoparticles are not as easy to detect as bigger chunks of metal and they do not reflect light the same way.