Bacterium turns poison into gold

Evidence of a bio-mineralization of gold by microbes

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The formation of gold was thought to be an abiotic process. But now an international research team has proven that the growth of gold nuggets can also be the result of an active biochemical process. Scientists also identified the genes involved in the bio-mineralization of gold, as reported in the online edition of the Proceedings of the National Academy of Sciences (PNAS).

The fact that microorganisms can play an important role in the formation of minerals on the earth's surface and also in the transport of metallic particles was already known. However, the formation of gold was considered a purely abiotic process. But then Australian scientists discovered the metal-resistant bacterium Cupriavidus metallidurans on gold nuggets - and this at two locations, which are 3, 500 kilometers apart. Was this a mere coincidence? Hardly likely.

An international research group headed by Frank Reith from the University of Adelaide in Australia decided to investigate. Scientists from the German Martin Luther University Halle-Wittenberg (MLU) were also involved because they have been dealing with this bacterium for years.

Microbial accumulation of toxic gold complexes

Research at the European Synchrotron Beam facility in Grenoble, France and the Argonne Laboratory in the US and high-energy X-rays, for example, revealed cell accumulation of clusters where the concentration of a toxic gold-sulfur complex was high.

Cell biological and genetic analysis, conducted by scientists led by Professor Dietrich Nies of the Institute of Biology at the University of Halle-Wittenberg, showed that the bacteria respond to the poison by turning on special genes that increase their resistance. The defense reactions of the unicellular organisms in turn trigger a reaction chain, in the course of which the gold complex is changed so that non-toxic gold-carbon complexes and atomic gold are formed. display

New impulses for biotechnical applications

"Minerals are constantly being rebuilt in nature, primary ones are becoming secondary - and very low concentration but toxic mixtures of gold can become metallic gold, " explains Nies. This so-called bio-mineralization of gold, ie the formation of gold by the influence of bacteria, according to the researchers could open up completely new horizons in the biotechnological application of bacteria. "Perhaps the knowledge gained now will allow gold to be extracted even from gold-poor solutions, " says the researcher.

(University of Halle, 09.10.2009 - NPO)