From dirt to gold- a peculiar new use of fungi

By Hanna Zafar

Gold to this day is still one of the most pursued precious metals. It’s rarer than copper and silver, plus increasing in value through the years. But due to its rarity, it is difficult to retrieve from the earths crust. What if there was a way to decrease the use of mining and use Earth’s natural resource to obtain gold from a difficult environment?

A 3-year study carried out by Dr Tsing Bohu and his colleagues in Commonwealth Scientific and Industrial Research Organisation (CSIRO) Mineral Resources in collaboration with University of Western Australia, found microbes can be used to retrieve gold. Fungi present near Boddington, south of Perth, can oxidise the metal, Dr Bohu et al reported in Nature Communications. In this study, the researchers sampled the surface soil of the region they named in the paper as a gold ‘hot spot’, and scanned for microbes that could be playing a role in oxidising the gold. From this they found four gold-oxidising fungal isolates, one of which was a strain of Fusarium oxysporum, that has not been previously reported in playing a role in oxidising metals. This fungus has been found to dissolve the gold using superoxide, following which it precipitates nanoparticles of the metal onto the surface. This process could help move the gold from the deeper parts of the Earth’s crust closer to the surface.

“Fungi are well-known for playing an essential role in the degregation and recycling of organic material, such as leaves and bark, as well as for the cycling of other metals, including aluminium, iron, manganese and calcium,” Dr Bahu tells the Australian Associated Press, “But gold is so chemically inactive that this interaction is both unusual and surprising- it had to be seen to be believed”. The results from this study represent a formerly unidentified role for fungi in biogeochemical cycling. Previous studies have shown the bacteria Cupriavidus metallidurans playing a role in interacting with gold, which helped understanding microbe’s roles with metals. Dr Bahu and collegues did look into how fungi and bacteria responded to gold in the environment, and found fungi communities to be influenced with gold while bacteria did not.

So why is there so much attention going around about this paper? Dr Bahu has said that the fungus could be an indicator of where gold is in the soil. This is important as it will help gold miners in specifying where to dig. This would reduce the environmental impact of gold mining and damaging waste, while also extracting the gold in a less harmful way. But don’t rush out searching for a gold-studded fungus just yet. This specific fungus cannot be seen with the naked eye and requires a microscope. Hopefully in the near future, scientists will bring us closer to making fungal gold extraction a bright and expensive reality.


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