Not much good can be said about Berkeley Pit in Butte, Montana. It’s an abandoned open pit copper mine, one mile long, a half-mile wide, third of a mile deep, and it contains some of the most toxic water on the planet.

No fish swim in Berkeley Pit, no plants line its shores, and landing on the water’s surface can be fatal to birds.

And it might yield new treatments for cancer.

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Berkeley Pit opened as a mine in 1955, and over the years more than one billion tons of material was extracted. Copper was its primary product, but gold and silver were also mined there.

Eventually, falling copper prices made the mine too expensive to operate and it was closed on April 22, 1982—Earth Day, coincidentally. When mining operations ceased, groundwater began filling the pit, rising as fast as a foot per month and leaching metals from the sides of the pit. Besides copper, the water is loaded with arsenic, cadmium, zinc, cobalt, and other metals, giving it a pH of 2.5, about the same acidity as lemon juice or cola. Iron gives the surface water a reddish hue; go a little deeper, copper turns the water green.

In 1995, a migrating flock of snow geese landed in Berkeley Pit, staying there for several days as they waited out a storm. More than 300 died, and necropsy showed that their throats had been burned by the toxic compounds in the water.

The rising water in Berkeley Pit threatens to contaminate the nearby groundwater, making it one of the Environmental Protection Agency’s most dangerous Superfund sites—polluted locations requiring a long-term response to clean up hazardous material contaminations. As the water approaches the critical level where spillover into the aquifer will occur, pumps will go into operation to remove water from the pit.

It was long thought that no life of any kind could survive in Berkeley Pit, but in 1995 a small clump of greenish matter was retrieved from the water and delivered to the husband-wife research team Andrea and Don Stierle, biochemists who are now associated with the University of Montana. The Stierles identified the mass as the single-celled algae Euglena mutabilis, an extremophile that is able to tolerate exposure to high concentrations of toxins.

The Stierles specialize in isolating and characterizing compounds with potent, selected biological activity from micro- and macro-organisms. Earlier, they had discovered a microscopic fungus that lives in tree bark and produces paclitaxel. When they realized that Berkeley Pit harbors life, they set to work with a team of students, collecting water samples, isolating microorganisms, and culturing them.

Among the organisms the Stierles identified was a new species of the fungus Penicillium rubrum, which was found to yield novel compounds that were dubbed berkeleydione, berkeleytrione, berkeleyacetals, and berkeleyamides, and which the Stierles have studied intensively.

Recently, they have investigated the potential of these and other Penicillium-derived compounds to influence the activation of pro-inflammatory interleukins, which are thought to interfere with the action of anticancer vaccines.1 Other compounds derived from Penicillium rubrum have exhibited selective activity against leukemia cell lines.2 Compounds derived from another extremophilic fungus found in Berkeley Pit, Penicillium solitum, were shown to inhibit the signal transduction enzymes caspase-1 and caspase-3 and to mitigate the production of interleukins in leukemia cell lines.3

Despite these successes, the Stierles don’t regard Berkeley Pit as simply a resource for producing bioactive compounds: another of their research interests is in using microbes found in the pit to help remediate this potential ecological disaster. Their focus is on an unusual yeast that sorbs metals even in conditions of extremely high acidity.

Berkeley Pit won’t be ready for swimming anytime soon, but its unusual inhabitants are likely to continue to yield interesting and potentially useful compounds for years to come.


1. Stierle DB, Stierle AA, Patacini B, McIntyre K, Girtsman T, Bolstad E. Berkeleyones and related meroterpenes from a deep water acid mine waste fungus that inhibit the production of interleukin 1-β from induced inflammasomes. J Nat Prod. 2011;74(10):2273–2277.

2. Stierle AA, Stierle DB, Girtsman T. Caspase-1 inhibitors from an extremophilic fungus that target specific leukemia cell lines. J Nat Prod. 2012;75(3):344–350.

3. Stierle DB, Stierle AA, Girtsman T, McIntyre K, Nichols J. Caspase-1 and 3 inhibiting drimane sesquiterpenoids from the extremophilic fungus, Penicillium solitum. J Nat Prod. 2012;75(2):262–266.