The bacterium Cupriavidus metallidurans survives in toxic environments by excreting solid 24-karat gold.

Cupriavidus metallidurans is a rod-shaped bacterium first isolated in 1976 at a metal-processing plant in Belgium. It is famous for its ability to survive in concentrations of heavy metals that would be fatal to other organisms. Researchers from the Martin Luther University of Halle-Wittenberg and the University of Adelaide published a definitive study in 2018 explaining this biological mechanism.The process begins when the bacterium encounters toxic gold complexes in the soil. To prevent these toxins from entering its central metabolism, the microbe uses an enzyme called CupA to pump copper out of the cell. Simultaneously, another enzyme named CopA transforms the dissolved gold ions into stable, metallic gold nanoparticles. This biochemical defense mechanism prevents the gold from interfering with the cell's internal chemistry.These solid gold particles, measuring only a few nanometers in size, are deposited on the exterior of the bacterial cell wall. Over thousands of years, these microscopic deposits accumulate to form the gold veins and nuggets found in nature. This discovery has significant implications for the 'biomining' industry, as it offers a non-toxic method for extracting precious metals from ore or electronic waste.Beyond gold, this bacterium is also being studied for its ability to process other rare elements. Its unique genetic makeup allows it to thrive in environments saturated with zinc, cadmium, and cobalt. By understanding how C. metallidurans manages these toxins, scientists hope to develop new technologies for cleaning up industrial pollution while recovering valuable resources.