These bacteria can literally ‘poop’ gold
A soil-dwelling bacterium, Cupriavidus metallidurans, can turn toxic gold ions into solid gold by using special enzymes. These microbes quite literally "poop" gold. The findings were published in Metallomics.
A strange species of bacteria has amazed scientists with its natural ability to transform toxic gold into solid gold nuggets... every time it breathes.
The bacteria, Cupriavidus metallidurans, live in soil packed with heavy metals. They’ve been studied for years because of their resistance to toxic environments. Now, researchers finally understand how these bacteria pull off what seems like a form of microbial alchemy.
In a study led by Dietrich Nies, a molecular microbiologist at Martin Luther University in Germany, scientists found that the bacteria use a set of special enzymes to manage harmful metals. The findings were published in the journal Metallomics in January 2018.
These rod-shaped microbes have two membranes. Between them is a space called the periplasm. Normally, they need tiny amounts of copper to survive, but too much of it can be toxic. To handle this, the bacteria use an enzyme named CupA, which pumps excess copper from the inner part of the cell into the periplasm, where it’s less harmful.
Things get tricky when the bacteria encounter gold ions. These ions — gold atoms that have lost electrons — are highly unstable and toxic. They easily slip through both cell membranes and enter the interior, where they interfere with normal cell functions. Worse still, these gold ions also block the CupA pump, making it harder for the bacteria to remove excess copper.
To survive this toxic mix, the bacteria activate another enzyme: CopA. This enzyme transfers electrons to both gold and copper ions. This neutralises them and turns them into stable metallic forms, which can no longer re-enter the cell or cause harm.
These newly formed gold nanoparticles get stuck in the periplasm and once it’s full, the bacteria’s outer membrane splits open and releases the gold outside — essentially pooping gold.
According to Nies, some of these bacteria end up coated in gold. Although the individual particles are tiny, they can clump together to form gold chunks the size of a grain of sand.
Researchers believe that understanding this process could lead to cleaner, safer ways to extract gold from ore. Currently, extracting gold from low-grade ore often involves mercury — a highly toxic chemical. If scientists could replicate the bacteria’s method, it could revolutionise the gold-mining industry.