Bioprospecting in the Berkeley pit: Bio active metabolites from acid mine waste extremophiles

Abstract

The Berkeley Pit Lake system in Butte, Montana is part of the largest EPA Superfiind site in North America. It includes Berkeley Pit Lake, an abandoned open-pit copper mine, 1300 feet deep and one mile across. During its thirty years of operation the Pit and surrounding deep shaft mines were dewatered through constant pumping. On Earth Day 1982 the pumps were turned off for the last time, and the Pit began to evolve into an acid mine waste lake. As infiltrating ground water continually seeps into the Pit, rich veins of pyrite and other minerals dissolve, generating acid in the process. There are currently 30 billion gallons of water in the Pit, with an inflow rate of 4 million gallons/day. The water is acidic (pH 2.5 - 2.7) and contaminated with high concentrations of metal sulfates including iron, copper, aluminum, cadmium and zinc. Unfortunately, the Pit Lake system sits at the headwaters of the Clark Fork River, a major tributary of the Columbia River. If the water rises another 200 feet, it will reach the critical overflow level. At the current rate of rise, the critical level will be reached in approximately ten years. Although the chemical dynamics and possible remediation strategies of the Pit Lake have been studied for twenty years, the microbial ecology was neglected. With its low pH and high metal content, it was considered too toxic to support life. Since 1995, however, with colleague Grant Mitman, we have isolated over sixty fungi, protists, algae, protozoans and bacteria. Although conditions within the Pit Lake System are toxic for “normal” aquatic biota, these same conditions represent an ideal environment for extremophiles. This hostile environment may also select for new species that produce novel secondary metabolites. It can be a challenge isolating and culturing these extremophiles, but it is the unique challenge of drug discovery to find methods for targeting the bioactive components in these organisms.