A team of CU-Boulder biologists led by Professor Norman Pace, one of the world's leading experts on molecular evolution and microbiology, published their report "Hydrogen and bioenergetics in the Yellowstone geothermal system" this week in the online edition of the Proceedings of the National Academy of Sciences.
The team's findings, based on several years of research at the park, refute the popular idea that sulfur is the main source of energy for tiny organisms living in thermal features.
"It was a surprise to find hydrogen was the main energy source for microbes in the hot springs," Pace said. "This project is also interesting in the context of microbiology because it's one of the few times we've been able to study microbes to get information on an entire ecosystem. That's never before been possible."
The study was specifically designed to determine the main source of metabolic energy that drives microbial communities in park features with temperatures above 158 degrees Fahrenheit. Photosynthesis is not known to occur above that temperature.
A combination of three different clues led researchers to conclude that hydrogen was the main source of energy. Genetic analysis of the varieties of microbes living in the hot springs communities revealed that they all prefer hydrogen as an energy source. They also observed ubiquitous H2 in all the hot springs at concentrations sufficient for microbial bioenergetics.
Thermodynamic models based on field data confirmed that hydrogen metabolism was the most likely fuel source in these environments.