Exploring the marine sediment environment’s influence on microbial sulfur isotope biosignatures using experimental evolution
Microbial metabolisms preferentially utilize substrate molecules containing lighter isotopes of elements. As a result of this preferential usage, from mineralized metabolites, we can place constraints on environmental conditions that influence metabolism over long periods of time. However, these constraints assume that a given microbial functional transformation has imparted the same quantitative isotopic partitioning in response to environment over time. The work presented here describes a series of experiments designed to test the hypothesis that microbial isotope fractionation is independent of microbial adaptation to environmental changes. Specifically I use experimental evolution to interrogate the effects of electron acceptor depletion, electron donor depletion, and a change from planktonic growth to biofilm-like growth. These challenges were selected to mimic those experienced by microbes deposited on the surface of marine sediments, and progressively buried as a result of sedimentation; or in the case of planktonic versus particle associated growth, to emulate global changes in seawater chemistry. The results of these studies suggest that microbial fractionation of isotopes is not independent of adaptation, and that the biosignatures that have been utilized in paleo reconstructions may also bear a signal of microbial adaptation.
I studied Biochemistry at Cornell as an undergraduate, Biological Oceanography at UW for my master’s, and Geobiology at McGill for my Ph.D. I was a C-DEBI postdoctoral fellow from 2017-2019 and am currently a NASA Astrobiology Postdoctoral Fellow working at the Colorado School of Mines with John Spear. I’ve been fascinated by all the interesting ways life can figure out how to persist and reproduce in all manners of environments for a long time. I love science outreach and communication, stinky mud, playing with my kids, and making lists.