LEXEN: Biogenic Fractionations of Transition Metal Isotopes: Novel Methods for the Examination of Life in Extreme Environments

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Professors Ariel D. Anbar and Kenneth H. Nealson, of the Department of Earth and Environmental Sciences at the University of Rochester, are supported by the Division of Chemistry, the Office of Multidisciplinary Activities of the Mathematical and Physical Sciences Directorate, the Directorate for Biological Sciences, and the Division of Earth Sciences for their studies of the biogenic fractionation of transition metal isotopes. These studies test the hypothesis that fractionation of stable isotopes of key metabolic metals occurs during uptake and metabolism of these metals by microorganisms and that such isotope fractionation will leave a recognizable signature that will be useful for the study of life in environments where extreme conditions preclude the application of other biomarkers. Professors Anbar and Nealson use multiple-collector inductively-coupled plasma mass spectrometry to characterize the isotopic compositions of metals isolated from microorganisms sampled in the field and from microbes cultured under controlled laboratory conditions. Their studies are focused on the kinetic fractionation of the isotopes of copper and zinc, expected during the enzyme-catalyzed uptake of these metals, and of iron, expected during microbially-mediated redox reactions. These biogenic isotope fractionations are expected to provide information about the presence or absence of biological activity in general and about specific metabolic processes in particular. Fractionation of stable isotopes of carbon, nitrogen, and sulfur due to the different reaction rates of compounds containing different isotopes of these elements have been used for years to obtain information about metabolic processes in environments not accessible to direct observation. With the support of the Division of Chemistry, the Office of Multidisciplinary Activities of the Mathematical and Physical Sciences Directorate, the Directorate for Biological Sciences, and the Division of Earth Sciences, Professors Ariel D. Anbar and Kenneth H. Nealson, of the Department of Earth and Environmental Sciences at the University of Rochester, are developing techniques to explore the biogenic fractionation of isotopes of metals which play key roles in metabolic processes. By analyzing the fractionation of isotopes of copper, zinc, and iron, Professors Anbar and Nealson obtain information about the presence or absence of biological activity in general and about specific metabolic processes in particular. These studies are of particular utility for the study of life in extreme environments, where extreme conditions preclude the application of other `biomarkers.` Such environments include modern settings which are physically remote or subject to extreme environmental conditions and ancient environments which can be studied only through the geological record.