All that Glitters is Gold: Bacteria Turns Toxic Metals into Gold Nuggets

In the world of biology, the rod-shaped bacterium Cupriavidus metallidurans is quite famous. This soil-living bacterium is able to survive massive doses of toxic metals. In 2009, scientists found these bacteria were capable to deposit solid gold into its immediate environment, but nobody knew how. Besides the fact that they could survive heavy metal environments that were toxic to biological organisms, the bacteria were also responsible for creating inert gold. Recently, the same science team finally understood the process and the existence of the gold nuggets.

Bacteria and Alchemy or How to Turn Toxic Gold into Shiny Gold Nuggets

The study Synergistic gold–copper detoxification at the core of gold biomineralisation in Cupriavidus metallidurans was published in the journal Metallomics. The authors found the answer to the gold dilemma literally surrounding the bacteria. They are surrounded by two membranes, with a space called the periplasm in between. Tin order to conduct their metabolic processes, the bacteria need trace amounts of copper, but in large doses, copper is highly toxic. In order to solve the problem, the bacteria use their special enzyme called CupA to pump excess copper from the interior of the cell into the periplasm, where it becomes harmless.

The magic and beauty of alchemy occurs when bacteria encounter gold ions. These are gold molecules that have lost one or more of their electrons and are therefore unstable. These ions travel into the interior of the cell as they can go past both cellular membranes. Once they reach the cell’s interior, they can cause severe damage on their own. These ions can also inhibit the CupA pump (the one responsible for getting rid of the excess copper) and are able to compound damage from copper ions that make their way into the cells.

The bacteria are lucky, however. They feature another enzyme called CopA. This enzyme steals electrons from the copper and gold ions, transforming them into stable metals, which cannot easily pass through the interior membrane of the cell. In other words, the bacteria form and immobilize metallic gold nanoparticles in their periplasm, which are less toxic.

The surreal phenomenon, however, is the “gold pooping”. In lack of a better term, the gold pooping is exactly what it sounds like. Once the periplasm is filled with enough inert gold, the outer membrane splits and spills out the shiny golden nuggets.

According to Dietrich Nies, a molecular microbiologist at Martin Luther University in Germany and one of the study’s authors who offered some statements for Live Science, “When confronted with ever more gold, some bacterial cells are completely encased with gold.”

If you think the bacteria produces full lingoes of gold, think again. The golden nuggets come in micrometers in size, but they can aggregate into sand-grain-size chunks.

Why are the Bacterial Golden Nuggets so Important?

Let us put it this way: people just found a way to naturally produce gold in a non-toxic, safe, and environmentally safe manner. If they can mimic the bacterial functioning on a larger scale, that it. In present, we use mercury to make gold, so to speak, but the process is highly toxic for the people working in such industries and the environment itself.

According to the study’s authors, we can change all that if we can reproduce the Cupriavidus metallidurans bacteria’s behavior. The organism essentially transforms solid gold into a highly soluble gold compound and then back again into solid, stable golden nuggets. If we could mimic the process, it would be possible to mine ore with a very low percentage of gold, transform the precious metal into a water-soluble version of itself, dissolve it from the rock and then turn it back into solid gold. We can thus further use this particular solid gold to make everything from jewelry to electronic components.

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William E. Eubanks
 

I'm one of the main writers on the site; mostly dealing with environmental news and ways to live green. My goal is to educate others about this great planet, and the ways we can help to protect it.

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