The Gold-Making Bacterium That Turns Toxic Metals into Metallic Gold

Cupriavidus metallidurans, a metal-resistant bacterium turning toxic gold ions into metallic gold nanoparticles while surviving copper stress. Illustration by the author.

Cupriavidus metallidurans is a metal-resistant bacterium that thrives in environments rich in toxic metals. Remarkably, it can transform toxic gold ions into metallic gold nanoparticles, a process that helps detoxify its surroundings. This ability , known as biomineralisation, allows the bacterium to survive in soils contaminated with gold and other heavy metals .

A recent study in 2024 by Hirth and colleagues looked at how C. metallidurans responds to both gold and copper ions. They found that each gold species can influence the ability of the bacterium to cope with metal stress, and the presence of copper ions produces synergistic toxicity , which challenges its resistance systems .

Key to its survival is glutathione, an antioxidant that enables the bacterium to manage metal stress. Genes like gig, involved in metal resistance, are only activated when glutathione is present. Another important player is the periplasmic oxidase CopA, which helps reduce cellular levels of gold and copper, maintaining metal balance .

These insights reveal the sophisticated strategies C. metallidurans uses to survive in extreme environments. Understanding these mechanisms has practical implications for bioremediation, offering potential ways to detoxify metal-contaminated sites while naturally managing toxic gold ions .

Reference:
Hirth, N., Wiesemann, N., Krüger, S., Gerlach, M.-S., Preußner, K., Galea, D., Herzberg, M., Große, C., & Nies, D. H. (2024). A gold speciation that adds a second layer to synergistic gold–copper toxicity in Cupriavidus metallidurans. Applied and Environmental Microbiology, 90(4), e0014624. https://doi.org/10.1128/aem.00146-24