A University of Maryland researcher and colleagues found a fungus that removes mercury from the soil around plant roots. The researchers genetically engineered the fungus to make it excrete more mercury.
Public health is at risk due to mercury pollution of soil and water. According to the new work, Metarhizium could provide an inexpensive and efficient way to protect crops from pollution.
The study was published in the Proceedings of the National Academy of Sciences.
According to St. Leger, Metarhizium stops plants from taking up mercury. The plant thrives despite being planted in polluted soil. The mercury can be quickly cleared from both fresh and saltwater.
The St. Leger laboratory has shown that Metarhizium colonizes plant roots and protects them from insect pests. Scientists have known for a long time that Metarhizium is found in soils that have been polluted by mercury mines. It was not known how the fungus survived in mercury polluted soils, or if that had implications for the plants the fungus normally lives with.
Two genes that are very similar to genes present in a bacterium known to detoxify, or bioremediate, mercury, are found in the genomes of Metarhizium.
For the current study, the researchers ran a variety of laboratory experiments and found that corn with Metarhizium was just as good if it was planted in clean soil or mercury-laden soil. There was no mercury in the plant tissues of the corn.
Two genes that were similar to those in mercury remediatingbacteria were removed by the researchers. Corn plants were not protected from mercury-laden soil when they replicated their experiment.
The genes were inserted into a fungus that does not normally protect corn from mercury. Plants were protected from mercury-laden soil by the newly modified fungus.
Microbiological analyses show that the genes in question are involved in breaking down highly toxic organic forms of mercury into less toxic, non-toxic mercury molecule. The researchers genetically engineered Metarhizium to express more of the detoxify genes.
The researchers were able to clear mercury from fresh and salt water in 48 hours.
Experiments will be conducted in China to see if Metarhizium can turn toxic environments into productive fields for corn and other crops. Current methods of remediating polluted soils involve removing toxins from entire fields before anything can be planted. It can cost a lot and take a long time. The plants can't take up the toxins in the soil because Metarhizium is so effective.
The fungus protects its plant home by allowing it to grow in mercury-rich environments. The only microbe we know of with the ability to be used like this is the one that doesn't grow on Plants. You can plant crops that are protected from mercury-rich soils by dipping seeds in Meta rhizium.
In addition to its potential as a cost-effective tool for reclaiming polluted lands for agriculture, Metarhizium may help clear mercury from wetlands and polluted waterways that are increasingly threatened by mercury pollution due to climate change and melting permafrost.
There is more information about the bioremediation of mercury-polluted soil and water by the plant symbiotic Fungus Metarhizium robertsii. 10.1073/pnas.
Journal information: Proceedings of the National Academy of Sciences
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