"Past research had shown that there is a consortia of these two very different single-celled organisms, and indirect tests indicated they might be the source of methane consumption," said Dr. Christopher H. House, assistant professor of geosciences at Penn State. "We decided to directly test if these organisms are responsible."

The research team explains their approach in today's (July 20) issue of the journal Science. Research team members Victoria J. Orphan, graduate student, and Dr. Edward F. Delong, chair of the science department at Monterey Bay Aquarium Research Institute, were responsible for identifying the organisms in the consortia. The sulfate-reducing bacteria, Desulfosarcina, and the methane-consuming archaeobacteria, Methanosarcinales, were tagged with flouresent dyes that attach only to individually specific genetic material. In this way, one dye attached to the Desulfosarcina and another, of a different color, attached to the Methanosarcinales. Investigation under flourescent light showed the sulfate-eaters surrounding the methane eaters in an aggregated clump about the diameter of the width of a human hair.

"To determine that these aggregates were responsible for the methane consumption, we had to test the organisms to see which carbon isotopes were incorporated into the cells," says House at Penn State.

House and Orphan, working with Dr. Kevin D. McKeegan, professor of Earth and space sciences, University of California, Los Angeles, employed an ion probe that uses cesium ions focused to a very small spot to slowly erode the cells for study. The probe allowed samples of the carbon from the consortia to be tested, beginning with the outer cells and then tunnelling toward the middl
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Contact: A'ndrea Elyse Messer
aem1@psu.edu
814-865-9481
Penn State
19-Jul-2001