title: Intracellular metabolite levels shape sulfur isotope fractionation during microbial sulfate respiration.
abstract: We present a quantitative model for sulfur isotope fractionation accompanying bacterial and archaeal dissimilatory sulfate respiration. By incorporating independently available biochemical data, the model can reproduce a large number of recent experimental fractionation measurements with only three free parameters: (i) the sulfur isotope selectivity of sulfate uptake into the cytoplasm, (ii) the ratio of reduced to oxidized electron carriers supporting the respiration pathway, and (iii) the ratio of in vitro to in vivo levels of respiratory enzyme activity. Fractionation is influenced by all steps in the dissimilatory pathway, which means that environmental sulfate and sulfide levels control sulfur isotope fractionation through the proximate influence of intracellular metabolites. Although sulfur isotope fractionation is a phenotypic trait that appears to be strain specific, we show that it converges on near-thermodynamic behavior, even at micromolar sulfate levels, as long as intracellular sulfate reduction rates are low enough (<<1 fmol H2S⋅cell(-1)⋅d(-1)).
authors.affiliation: Department of Earth and Planetary Sciences and GEOTOP, McGill University, Montréal, QC, Canada H3A 0E8; and boswell.wing@mcgill.ca itay.halevy@weizmann.ac.il.
authors.forename: Boswell A
authors.initials: BA
authors.lastname: Wing
authors.affiliation: Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot 76100, Israel boswell.wing@mcgill.ca itay.halevy@weizmann.ac.il.
authors.forename: Itay
authors.initials: I
authors.lastname: Halevy
mesh_terms: D001105:Archaea / Q000378:metabolism*; D001419:Bacteria / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D008954:Models, Biological; D013460:Sulfur Isotopes / Q000145:classification / Q000378:metabolism*
chemical_list: D013460:Sulfur Isotopes
keywords: dissimilatory sulfate reduction; flux–force relationship; sulfur isotope fractionation