Bacteria and the Art of Purifying Gold

Here comes a surprise. Bacteria can purify gold. The discovery was made by scientists from Australia and is reported in the latest issue of journal Geology.

The catch is in a thin layer of microbes, known as a biofilm that is up to 40 μm thick, found enveloping gold grains in a Queensland mine. This biofilm dissolves the gold on contact and creates toxic gold ions that can break down the bacteria's cell walls. The bacteria fight back by transforming the ions into metallic gold nanoparticles. These nanoparticles later coalesce into lace-like crystals. This form of gold is much purer than the original gold grains. Original gold grains contain silver and mercury.

The researchers hope to genetically modify the bacteria to become much more efficient gold purifies.