Bacteria Excrete Nanoscale Gold Nuggets


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Could scientists one day be panning for gold in a Petri dish?

McMaster Univ. researchers have discovered that a gold-dwelling bacterium excretes a small molecule capable of forming solid gold.

Nathan Magarvey and his team have found the bacterium Delftia acidovorans can turn toxic, water-soluble gold – ions of the metal that are dissolved in water – into gold aggregates.

“It has long been known that Delftia acidovorans live on gold nuggets in biofilms, though how such bacteria avoid gold-mediated toxicity has been a mystery,” Magarvey says.

For the study, Magarvey and his students Chad Johnston, Morgan Wyatt, Ashraf Ibrahim and Xiang Li, as well as collaborators at Western Univ., grew a colony of Delftia acidovorans in the lab.

The team conducted tests to determine how it produces the molecular-sized gold nuggets outside its cell wall. They concluded the answer lies in a part with a molecule excreted by the microbe that both shields the organism and transforms the poisonous ions into particles.

“The bacterium precipitates the molecule and forms gold nanoparticles and tiny gold platelets that are essentially the seeds of gold nuggets, resembling those you would find in natural geological deposits. It is a novel mechanism for gold biomineralization, an extremely understudied but emerging field.”

Magarvey says the research, published in the journal Nature Chemical Biology, could one day be used to clean up waste water sites at gold mines, though that wasn’t the primary focus of the team’s work.

The findings also open doors to understanding the importance of natural, small molecules in the environment and in medicine.

“Our focus is on how bacteria make molecules and the benefits that these molecules may have in medicine and in their ecological settings. Our next targets are those bugs that live on or within us and realizing what roles human-associated bacteria and their metabolites play in our well-being and health.”

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