Treasure hunters may have an unexpected ally in bacteria. The secret lies in a thin layer of microbes, known as a biofilm, that researchers found enveloping gold grains in a Queensland mine. The biofilm dissolves the gold on contact, creating toxic gold ions that can break down the bacteria's cell walls. But the bacteria fight back by transforming the ions into metallic gold nanoparticles that later coalesce into lace-like crystals across the surface. This form of gold is much purer than the original gold grains, which also contain silver and mercury, and is thus much more attractive to miners, the team reports  this month in Geology. The researchers speculate if they could genetically modify the bacteria to fluoresce when they purify the gold, the bugs could become something even more important: Microbial metal detectors.
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