Ecosystem Function

Titan, Saturn’s largest moon, has a nitrogen-rich atmosphere with 2% methane and 3.5 ppm acetylene. Photo credit: NASA, Voyager 2

Our project began investigating acetylene (C2H2) fermentation nearly 30 years ago following a serendipitous discovery of acetylene consumption by San Francisco Bay sediments. A consortium of acetylene fermenters and sulfate reducers was capable of metabolizing acetylene through intermediates (acetaldehyde, ethanol, and acetate) to CO2, demonstrating the possibility of an acetylene-based anaerobic food chain that could have operated early in Earth’s history or presently on other acetylene-rich planets or moons in our Solar System. Others isolated an organism (Pelobacter acetylenicus) capable of growth on acetylene and identified the enzyme (acetylene hydratase, AH) responsible for the first step in degradation to acetaldehyde. These studies were revived when Ron Oremland and Mary Voytek (USGS, Reston) obtained a NASA grant to study the diversity of acetylene fermenters and to further investigate the significance of acetylene degradation by bacteria. Larry Miller and Shaun Baesman in Oremland’s group have re-isolated acetylene degraders from San Francisco Bay and also from freshwater Searsville Lake. Julie Kirshtein in Voytek’s lab developed primers based on these organisms that are used to probe likely environments for the presence of organisms which contain genes that regulate the activity of AH. Work is ongoing to determine the concentration limits of acetylene degradation and to explore other environments for this activity using culture-based and genomic techniques.

For more information see:

Oremland, R.S., and Voytek, M.A., 2008, Acetylene as fast food: Implications for development of life on anoxic primordial Earth and in the outer solar system: Astrobiology, v. 8, no. 1, p. 45-58 (on-line abstract )

Or go to: Microbial Biogeochemistry of Aquatic Environments

Also contact Ronald S. Oremland, Menlo Park Regional Office and Mary Voytek, Voytek Microbiology.

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