[Seminar] What can the sulfur isotope fractionation associated with dissimilatory sulfite reductase tell us about the redox evolution of Earth’s atmosphere?
William D. Leavitt, Harvard University
| When |
28 Oct, 2013
from
11:00 am to 12:00 pm |
|---|---|
| Where | Room 2.13 |
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Seminar
Title: What can the sulfur isotope fractionation associated with dissimilatory sulfite reductase tell us about the redox evolution of Earth’s atmosphere?
Speaker: William D. Leavitt
Affiliation: Harvard University, Department of Earth & Planetary Science, Cambridge, MA, USA
Abstract:
Experimental data using purified enzymes from sulfate reducing microorganisms (this work), coupled with data from cell-free extracts (Ford, 1957; Kemp & Thode, 1968), allow us to constrain the key mass-dependent sulfur isotope (m = 32, 33, 34, & 36) fractionating steps within the dissimilatory sulfate reduction metabolism. Sulfate reduction is critical to global sulfur cycling, and enzyme-specific fractionation factors provide fundamental boundary conditions to metabolic isotope models. Ultimately, the magnitude and variance of sedimentary (geological) S isotope values will be better understood, and past environmental histories more accurately reconstructed—e.g. the history of atmospheric oxygen mass and flux (c.f. H.D. Holland, 1973). Still, further enzyme- and cellular-scale experiments are needed—in sulfate reducers, sulfide oxidizers, and intermediate valence disproportionators—before global biogeochemical sulfur cycle models be predictive.
