Directly quantifying the isotopic fractionation associated with the key enzymes in microbial sulfate reduction

Harvard University, Cambridge MA

Investigators

Abstract

The microbial lifestyle of sulfate reduction is central to the oxidation of organic matter both in the Modern and throughout Earth?s history. This linkage to the carbon cycle, and in turn climate, is commonly inferred through sulfur isotope studies, which are themselves informed by experiments with extant bacteria that perform this process. At its core, however, bacteria are driven by a suite of enzymes, or catalysts, that conduct much of the critical chemistry. In this proposal, investigators look to place the first direct isotopic constraints on the two key enzymatic steps within this metabolism: dissimilatory sulfite reductase [DsrAB/C] and APS oxido-reductase [APSr]. This data will allow for a more mechanistic understanding of cellular fractionation processes, which will then sharpen our capacity to read environmental records. This research project will be conducted in collaboration with Dr. Ines Pereira of the Instituto De Technologia Quimica E Biologica, ITQB, Portugal, who will provide the biochemistry expertise necessary for the project. A Harvard graduate student will travel between the Pereira and Johnston's labs, acquiring valuable interdisciplinary training in isotope geochemistry and biochemistry. Travel costs for the international component of this research have been provided by the NSF Office of International Science and Engineering.