The Pit of Death and Life

Just outside Butte, Montana lies a pit of greenish poison a mile and a half wide and over a third of a mile deep. It hasn't always been so - it was once a thriving copper mine appropriately dubbed “The Richest Hill in the World.” Over a billion tons of copper ore, silver, gold, and other metals were extracted from the rock of southwestern Montana, making the mining town of Butte one of the richest communities in the country, as well as feeding America’s industrial might for nearly a hundred years. By the middle of the twentieth century, the Anaconda Mining Company was in charge of virtually all the mining operations. When running underground mines became too costly in the 1950’s, Anaconda switched to the drastic but effective methods of “mountaintop removal” and open pit mining. Huge amounts of copper were needed to satisfy the growing demand for radios, televisions, telephones, automobiles, computers, and all the other equipment of America’s post-war boom. As more and more rock was excavated, groundwater began to seep into the pit, and pumps had to be installed to keep it from slowly flooding.

By 1983, the hill was so exhausted that the Anaconda Mining Company was no longer able to extract minerals in profitable amounts. They packed up all the equipment that they could move, shut down the water pumps, and moved on to more lucrative scraps of Earth. Without the pumps, rain and groundwater gradually began to collect in the pit, leaching out the metals and minerals in the surrounding rock. The water became as acidic as lemon juice, creating a toxic brew of heavy metal poisons including arsenic, lead, and zinc. No fish live there, and no plants line the shores. There aren’t even any insects buzzing about. The Berkeley Pit had become one of the deadliest places on earth, too toxic even for microorganisms. Or so it was thought.

In 1995, an analytic chemist named William Chatham saw something unusual in the allegedly lifeless lake: a small clump of green slime floating on the water's surface. He snagged a sample and brought it to biologist Grant Mitman at the nearby Montana Tech campus of the University of Montana, where Mitman found to his amazement that the goop was a mass of single-celled algae. He called in fellow Tech faculty Andrea and Don Stierle, experts in the biochemistry of microorganisms. The Stierles had recently been trekking about the northwest, looking for cancer-fighting compounds in local fungi with great success. Coincidentally, the Stierles’ funding had just run out, and they needed a new project. They leapt at the opportunity to study these bizarre organisms.

After examining the slime under a microscope, the researchers identified it as Euglena mutabilis, a protozoan which has the remarkable ability of being able to survive in the toxic waters of the Berkeley Pit by altering its local environment to something more hospitable. Through photosynthesis, it increases the oxygen level in the water, which causes dissolved metals to oxidize and precipitate out. In addition, it pulls iron out of the water and sequesters it inside of itself. This makes it a classic example of an extremophile.

Euglena mutabilis

Extremophiles are organisms that can tolerate and even thrive in environments that will destroy most other living things. Some can even repair their own damaged DNA, a trait which makes them extremely interesting to cancer researchers. The Stierles reasoned that where there’s one extremophile, there may be others – most likely blown in by the wind. Given their previous successes with strange microorganisms, the researchers believed that the Berkeley Pit and its fledgling extremophile population could produce some medically useful chemicals.