Johnston, David TLeavitt, William2014-06-062014-06-062014Leavitt, William Davie. 2014. On the mechanisms of sulfur isotope fractionation during microbial sulfate reduction. Doctoral dissertation, Harvard University.http://dissertations.umi.com/gsas.harvard:11511http://nrs.harvard.edu/urn-3:HUL.InstRepos:12274566Underlying all applications of sulfur isotope analyses is our understanding of isotope systematics. This dissertation tests some fundamental assumptions and assertions, drawn from equilibrium theory and a diverse body of empirical work on biochemical kinetics, as applied to the multiple sulfur isotope systematics of microbial sulfate reduction. I take a reductionist approach, both in the questions addressed and experimental approaches employed. This allows for a mechanistic, physically consistent interpretation of geological and biological sulfur isotope records. The goal of my work here is to allow interpreters a more biologically, chemically and physically parsimonious framework to decipher the signals coded in modern and ancient sulfur isotope records.en-USGeochemistryGeobiologyMicrobiologyenzyme isotope fractionationgeomicrobial kinetic isotope effectsmicrobial sulfate reductionmultiple sulfur isotopesPhanerozoic oxygensulfur cycleThesis or Dissertation2015-06-04