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In an out-of-the-way corner of the 5,000-foot level, near the Horseshoe Sump, the heat and humidity were high enough to instantly fog safety glasses and camera lenses. Still, it wasn't quite hot enough for Rajesh Sani. "Is there any place hotter?" he asked Sanford Lab science liaison Tom Trancynger, who was escorting this recent expedition. Not on the 5000 Level, Trancynger explained, but he did have some suggestions for a future expedition on the 4850 Level.

Sani is a microbiologist at South Dakota School of Mines and Technology. A couple of weeks ago, Sani and his colleague, Aditya Bhalla, a doctoral student at SDSMT, went underground to collect samples of microorganisms. It was their first trip to the 5000 Level, but it wasn't Sani's first expedition to the Sanford Lab. "For the past five years we've been looking for thermophilic organisms to break down lignocellulosic materials into sugars," he said.  (Translation: "Thermophilic" organisms are creatures that thrive in extreme heat."Lignocellulosic" materials are plant-based materials containing "lignin." They can include wood products or crops, such as corn stover.)

Thermophilic organisms could be used to produce biofuels more efficiently. They also might be used to produce environmentally friendly bio-plastics that can break down harmlessly after they are used, or they might help remove contaminants from the environment.

Sani and his colleagues have already published five research papers on microorganisms deep in the Sanford Lab, and two more papers are under review. In the process, they've identified more than 8,600 separate underground organisms here. About 85 percent of them are novel. In other words, there's a lot of life underground. Some of the microbes they've found are the result of contamination from the surface. Others are unique to the underground. Still others are hybrids—the result of "horizontal gene transfers."

Though the temperature in this corner of the 5000 Level was pushing 90 degrees F., Sani would have preferred something closer to 140 F., which is the rock temperature at the 8000 Level. Still, he hoped that the 'PhyloChip' DNA microarray would reveal an interesting bug in this sample. "Our main goal is to find hyper-thermophiles," he said.