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Metal-Eating Bacteria Devours a Nail in Just Three Days

Can metal-eating bacteria clean up the highly polluting mining industry?

Mining pollution, when not properly dealt with, can have devastating effects on the environment: Mine waste, heavy metals, and acidic water often find their way to streams and rivers, polluting the headwaters of more than 40 percent of Western watersheds. In fact, according to the EPA, metal mines generated nearly 2 billion pounds of toxic waste in just 2017.

In response to this growing problem, a team of researchers led by biotechnologist Nadac Reales from Chile may have discovered a possible solution that could help clean up the country's highly polluting mining industry by demonstrating that a special type of bacteria can eat a nail in three days when it's starving, per Phys.org.

Chile is the world's leading copper producer, accounting for up to 15 percent of the country's GDP. Consequently, there is a lot of mining waste that pollutes the environment, which is why it could definitely use some help controlling it. If the technique could somehow be scaled up with proper investments, it could help the rest of the world as well.

Feeding bacteria while helping the world

The newly discovered method involves extremophiles, which are microorganisms that can survive and thrive in the harshest of environments. Reales and her team concentrated on an iron-oxidizing bacteria known as Leptospirillum that she isolated from the Tatio geysers, which are located 13,779 feet (4,200 meters) above sea level and some 220 miles (350 kilometers) from Antofagasta.

In addition to having an appetite for metals, Leptospirillum is also used in industrial bioleaching, the conversion of metals to a soluble form, and bio-oxidation, the extraction of metals. They thrive in an acidic environment where relatively large quantities of most metals have no effect, and when the experiments began, it took them two months to "eat" through a nail. The researchers wanted to take this to the next level, and the upshot of two years of testing was a significant rise in the speed with a nail being devoured in only three days.

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Of course, the bacteria are not harmful to humans or the environment, as seen in the chemical and microbiological tests that were conducted. When this disintegration process is complete, what's left is a crimson liquid residue known as a lixiviant, which has a surprise quality all its own. According to the researchers, this liquid can "improve the recovery of copper in a process called hydrometallurgy." The liquid residue can be utilized to remove copper from rock in a more environmentally friendly way than the present chemical leaching method, and thanks to this, green mining is "absolutely doable," says Reale.

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