Bacteria eat toxic metals and emit gold

Scientists discovered a bacterium capable of eating toxic metal compounds that still thrive, while emitting gold.

No life form on our planet can penetrate every successful environment like microbial cells. Among their many roles in life on Earth, some bacteria are capable of refining precious metals, according to Science Alert.

Like many other elements, gold can circulate in a biochemical cycle including: disintegrating, moving around and eventually re-concentrating in Earth's sediments. Microorganisms participate in all steps of this process. This led scientists to question how they were not poisoned by highly toxic compounds formed from gold ions in the soil.

Gold particles on the surface of bacteria C. metallidurans.

Frank Reith and colleagues at the University of Adelaide, Australia, for the first time discovered C. metallidurans-shaped bacteria that excreted gold in 2009. It could eat toxic gold compounds and turn them into metallic forms. of gold without any danger to the body. After many years of research, Reith knew exactly the mechanism and the way C. metallidurans used to do this. The results of the study are published in the journal Metallomics on January 2.

C. metallidurans thrives in soil containing both hydrogen and a variety of toxic heavy metals. This means that C. metallidurans does not have to compete with other organisms."If an organism decides to survive there, it must find a way to protect itself from these harmful substances," Dietrich H. Nies, microbiologist at Martin Luther University Halle-Wittenberg (MLU). , Germany, said.

C. metallidurans has an ingenious defense mechanism that involves not only gold but also copper. The compounds containing both of these elements can easily penetrate into C. metallidurans cells. When copper ions and gold complexes penetrate deep inside, they will cause devastating effects on bacteria.

To solve this problem, C. metallidurans uses CupA enzymes to transport copper out of the cell. But the presence of gold causes a new problem."In the presence of gold compounds, CupA enzymes are inhibited, which causes the compounds of copper and gold to remain in bacterial cells , " Nies said.

At this time, many other bacteria probably gave up and went to live in a less toxic place, but C. metallidurans did not. This organism has another enzyme called CopA that helps bacteria convert the compounds of gold and copper into a form that is not easily absorbed by cells.

"This ensures that there are fewer copper and gold compounds entering the bacterial cells. The bacteria are less poisoned and enzymes can help eliminate excess copper without obstacles." , Nies explained.

This process not only helps C. metallidurans remove unwanted copper, it also creates tiny gold nanoparticles on the surface of bacteria. Understanding how C. metallidurans can excrete gold will help scientists get closer to unlocking the biochemical cycle of gold. In the future, these insights can be used to refine precious metals from ores that contain only a small amount of metal.