Fournier Lab: Geobiology at MIT

Our research focuses on using genomic and phylogenetic insight to understand major events in planetary history, and reconstructing the deep origins of the earliest living systems.

There are only two preserved records of events on the early Earth: one preserved within rocks, and one preserved within the inherited genomes of extant lineages of organisms. Using gene phylogenies, molecular clocks, and novel approaches to date calibration, our lab seeks to read the newly revealed genome record and reconcile it with the geological record. Horizontal Gene Transfer (HGT) plays a strong role in this approach, as the transfer of genes between lineages permits the use of stratigraphic inference to determine the relative ordering of these groups in time. Similarly, transfer events can propagate fossil date calibrations from one branch of the Tree of Life to another.

Many groups of microbes have metabolisms that are intimately connected to major geochemical processes on Earth, such as the carbon, sulfur, and nitrogen cycles, or the production of oxygen via photosynthesis. Understanding the timing of the evolution and diversification of these microbes therefore allows us to more precisely infer how biological and geological processes co-evolved on Earth. In turn, this knowledge allows us to better infer the prevailing conditions of the continents, oceans, and atmospheres across deep time, and reconstruct a much richer narrative of the history of our inhabited planet. As such a history is key to understanding habitability in general, it is a central theme of Astrobiology research.


Ongoing Projects

  • Developing novel techniques for dating molecular phylogenies using reticulate genetic information, such as horizontal gene transfer and gene duplications
  • Estimating divergence times of diverse microbial groups, including Cyanobacteria, Proteobacteria, anoxygenic microbial phototrophs, methanogens, sulfur cycle bacteria, and nitrogen cycle bacteria
  • Mapping and dating the co-evolution of marine microbial metabolisms and substrate availability, such as the history of dimethyl sulfide production and utilization by eukaryotic algae, bacteria, and methanogens in marine systems
  • Mapping the adaptation to oxygenated environments within microbial genomes, through the distribution and evolutionary history of oxygen-related gene families
  • Using arthropod fossil calibrations to propagate date constraints to microbial lineages containing co-evolving symbiont lineages
  • Detecting partial HGT events within conserved gene families and determining their impact on phylogenetic reconstruction