Isotopic Fingerprints of Sulfur Metabolisms: Using the Minor Isotopes to Distinguish Between Process

Presenter: David Johnston, Harvard University
When: May 10, 2004 1PM PDT

Here we report sulfur multiple-isotope measurements of the hydrogen sulfide
and sulfate associated with dissimilatory sulfate reducing bacteria, sulfite
disproportionating bacteria, and sulfur disproportionating bacteria. These
experimental results confirm our prior findings and are consistent with our
prior interpretations of sulfate reduction by A. fulgidus (see Farquhar et
al., 2003). Further, they highlight the isotopic variability that metabolic
systems can produce. Our modeling efforts explain how these flow networks
function and why minor isotope signatures vary. These findings further
support that minor isotope signatures are representative of the biological,
or abiological pathway they are produced by. This insight, coupled with
recent increases in mass spectrometer precisions, allows us to analytically
resolve these signatures. We suggest that it will be possible use the minor
isotopes of sulfur to identify and differentiate between sulfur metabolisms
in the geological and planetary records.

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