OCGC Seminar - André Pellerin


Evolutionary Processes Affect Sulfur Isotope Signatures 


Mr. André Pellerin
Ph.D. Candidate
Department of Earth and Planetary Sciences
McGill University


Thursday, October 9th, 2014
11:30 a.m.
233 Advanced Research Complex (ARC) 
University of Ottawa 


Sulfur isotope fractionation during dissimilatory sulfate reduction is controlled by the energy metabolism of sulfate reducing microorganisms. While this metabolism responds to variability in the local environment, it is ultimately dependent on the underlying genotype. Since genotype and environment have both changed throughout Earth’s history, the geological record of biogenic S isotopes reflects the influence of environmental and evolutionary change. However, the basic interplay between microbial evolution and S isotope fractionation has not been examined. In this seminar, I will discuss some of the results from our evolution experiments with pure cultures of Desulfovibrio vulgaris Hildenborough and Desulfomicrobium baculatum. These experiments attempt to understand the role of evolutionary adaptation in controlling sulfur isotope fractionation. For instance, we demonstrate that over a timescale of hundreds of generations, the isotope fractionation imparted by Desulfomicrobium baculatum changes from 15‰ to 12‰ as its fitness in a new environment increases. Our observations suggest that the evolutionary trajectory of S isotope fractionation correlates with the magnitude of evolutionary adaptation to a specific environment. Thus, important metabolic information about the evolution of dissimilatory sulfate reduction may have been preserved in the sulfur isotope rock record in addition to, or in spite of, the environmental information.