Researchers Identify Fungus That Eliminates Toxic Mercury from Soil and Water

Mercury pollution of soil and water is a threat to public health all over the world. But researchers at the University of Maryland have found a potential new solution: a fungus that can eliminate the toxin. Metarhizium robertsii is a fungus that colonizes plant roots and protects them from herbivorous insects. Scientists already knew that this fungus was one of the only living things found in soils from toxic sites like mercury mines – but now, the implications for public health are becoming clear.

What did the experiments look like?

UMD entomology professor Raymond St. Leger and his fellow researchers ran several experiments and found that corn infected with the fungus grew just as well regardless of whether it was planted in clean soil or mercy-laden soil. Additionally, no mercury was present in the plant tissue of corn grown in soil polluted with mercury.

The researchers then genetically modified the fungi to remove the genes like those in mercy remediating bacteria. Modified Metarhizium wasn’t effective, and the corn plants died.

What did the research find?

Microbiological analysis revealed that the genes the researchers removed express enzymes that break down highly toxic organic forms of mercury into less toxic molecules. By leaving those genes in place, the fungus can break down toxic forms of mercy, allowing plants to grow even in contaminated soil. The researchers took it a step further and genetically engineered the fungus to express more of these detoxifying genes and increase production of the detoxifying enzymes as a result.

In a final experiment, the researchers found they could clear mercury from both fresh and saltwater by mixing in the fungus, and it often cleared these water sources within 48 hours. This means Metarhizium could be a cost-effective tool for reclaiming polluted lands, waterways, and wetlands.

What comes next?

The next step will be to conduct field experiments to see if the fungus can turn toxic environments into productive fields for crops. Currently, remediating polluted soils requires toxins to be removed or neutralized from an entire field before planting anything. Metarhizium, on the other hand, simply detoxifies the soil around the plant roots, preventing plants from taking up the toxin in the first place. This could be a game-changing development for polluted fields that need decontaminating. Additionally, the fungus could help clear mercury from wetlands and waterways, especially as climate change and melting permafrost increase the release of toxic metals like mercury into our water sources.

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