Rock-Eating Bacteria "Mine" Valuable Metals

Tim Hornyak in Tokyo
for National Geographic News
November 5, 2008

Bacteria can leach small amounts of valuable metals from otherwise useless ore, and scientists are now applying the latest biotechnology to make the bugs better miners.

These mineral-crunching microorganisms are a type of bacteria that use minerals as their source of energy. When the life-forms break down the matter through metabolism, they squeeze out metal ores or concentrates combined with sulfur in a process called bioleaching.

The method is emerging as an increasingly important way to extract valuable minerals when conventional methods such as smelting can't do the job cheaply enough, experts say.

Development is also being spurred by the electronics industry's brisk global demand for copper.

"Certain microbes react to metal ions and help copper be leached out of low-quality ore," said Masaru Tomita of the Institute for Advanced Biosciences at Japan's Keio University.

"The ultimate goal is to establish biotechnologies to leach copper from this low-quality ore."

Bioleaching already currently accounts for an estimated 20 percent of the world's mined copper, and is in use at about 20 mines around the world.

Bioleaching

People have seen the results of microbial leaching in mine waters and rust-colored rivers for thousands of years, but it took until 1947 for bacteria to be identified as the cause.

(Related: "Rust-Breathing Bacteria: Miracle Microbes?" [April 12, 2004].)

That's when bacteria at a mine in Utah in the western United States were found to be responsible for bluish copper-bearing solutions leaking from piles of waste rock.

Since that discovery, dozens of other microorganisms useful for bioleaching have been found around the world, including in an uranium mine, a volcano, and a hot spring.

Continued on Next Page >>


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