That finding, said Robert J. Hamers, a UW-Madison professor of chemistry and a co-author of the Science study, was a surprise.
"Thiobacillus is not the controlling or predominant player" it was presumed to be, said Hamers. "Inside the mine, where most acid drainage is found, it is essentially undetectable."
On the other hand, Leptospirillum is a far more active player inside the mine, making up as much as 50 percent of all microbe species found in a vast network of underground tunnels.
The Wisconsin team explored two important environments at Iron Mountain where mining occurred both in above ground pits and in miles of tunnels below ground.
"There are two different types of environment, and geochemical conditions are different in both places," said Hamers. "This gave us an opportunity to study all the different conditions of acid mine drainage."
Results showed that Thiobacillus prefers moderate temperatures and lower levels of acidity. Leptospirillum survives at significantly higher concentrations of acidity and higher temperatures.
The fact that Leptospirillum thrives in such conditions, suggests its role in accelerating acid mine drainage is more significant because its chances of being in contact with the ore body are greater, said Hamers.
The study strongly suggests that "we can develop better models than the ones we currently have," said Edwards. "We can not only identify how many are there, but we can show where they are" in nature.
Funded by the National Science Foundation, the study was conducted by an interdisciplinary team involving chemists, geologists and biologists. Other co-authors of the study included Matthew Schrenk, Robert Goodman and Jilli
Contact: Katrina J. Edwards
University of Wisconsin-Madison