The intimate interaction between microbial life and earth leaves specific chemical signatures that record information on microbial activity, and paleo-environmental conditions. As a geobiologist, my goal is to interpret these signatures and reconstruct an accurate picture of paleo-environments and microbial communities, and the nature of their co-evolution through time. To date, I have focused on the sedimentary biogeochemical sulfur cycle and its main metabolic pathways: microbial sulfate reduction and microbial sulfur disproportionation. These run the reductive and oxidative branches of the sedimentary sulfur biogeochemical cycle, respectively. As such, they respond to and track the evolution of Earth’s surface redox conditions. Deconstructing the net preserved isotopic signature into its individual metabolic components requires a thorough understanding of the biochemistry of each, and of the environmental information enclosed in their specific sulfur isotopic signatures. For this, I apply a wide range of research tools. These include stable isotope geochemistry, environmental observations, pure culture microbial experiments (using both wild-type and deletion mutant strains), modeling of intracellular dynamics, and construction of three-dimensional models of crucial proteins in these key metabolic pathways.
For more details on current projects and a list of publications, please visit my website!
Alyssa is a senior concentrating in Chemistry and Earth and Planetary Sciences, with a secondary field in the Comparative Study of Religion. She joined the Johnston group in Summer 2014. Her thesis research involves evaluation of organic molecules as potential proxies for atmospheric oxygen isotopes.
Chloé-Rose is a senior at Harvard College concentrating in Organismic and Evolutionary Biology with a secondary field in Earth and Planetary Sciences, focusing on marine sciences. She joined the Johnston group in the summer of 2020 to work on a phylogenetic project tracing the metabolic consequences of oxygen reactive microbe species across marine and hot spring environments.
Ben is an isotope geochemist with diverse interests in the Earth sciences. In the Johnston Group, he is currently exploring questions surrounding the evolution of the atmosphere and biosphere over the most recent billion years of Earth history using a triple-oxygen isotope approach.
He received his Ph.D. from the University of Calgary in 2013 for developing a novel stable isotope approach for characterizing oil sands reservoir fluids, and was awarded a Vanier Canada Graduate Scholarship for his work. From 2002 to 2008 he attended McMaster University in Hamilton, Canada where he earned B.Sc. and M.Sc. degrees in Earth and Environmental Sciences. His research during this time focused on compound-specific isotope analysis of lipid biomarkers with application to environmental remediation and monitoring. From 2006 to 2010 Ben was part of the Pavilion Lake Research Project team, a NASA Exploration Analog site, and an international collaborative research project. The project provides insight into the earliest life on Earth, and aims to change the way humans explore outer space.
I’m a junior studying Earth and Planetary Sciences with a secondary in Educational Studies. I joined the Johnston group in the spring of 2019 as an undergraduate research assistant and am now beginning my senior thesis with the lab, conducting isotope analysis on sulfur-bearing hydrothermal vent minerals.