June 23, 2009

Nickel isotope may be microbe biomarker

U.S. and British scientists have determined nickel might be a useful isotopic marker to trace the origins of single cell organisms that produce methane.

Our data suggest significant potential in nickel stable isotopes for identifying and quantifying methanogenesis on the early Earth, said Vyllinniskii Cameron, a recent Penn State graduate and now a post-doctoral fellow at the University of Bristol. Little is known about the actual timing of the evolution of methane producing organisms or their metabolism. Nickel stable isotope fractionation may well prove to be the fundamental unambiguous trace metal biomarker for these methanogens.

Fractionation of an element into its component stable isotopes occurs because each isotope is slightly different in mass, researchers said. Since biological organisms tend to favor one isotope over another, the presence of a specific isotopic fraction can indicate a biological process took place.

It may be possible in the future to test organic rich sedimentary layers from 2.7 billion years ago to see if nickel isotopic fractionation occurred, said Associate Professor Christopher House, director of the Penn State Astrobiology Research Center, part of NASA's Astrobiology Institute. Because there are no known bacteria that are methanogenic "¦ perhaps such work can help pinpoint when these methane producing organisms came into being.

The scientists report their research in the online edition of the Proceedings of the National Academy of Sciences.