Fournier Lab: Geobiology at MIT
Current Research

Our major research focuses on bringing genomic/phylogenetic insight to understanding major events in planetary history, and reconstructing the deep origins of the earliest living systems. Many groups of microbes have metabolisms intimately connected to major geochemical processes on Earth, including the carbon cycle, sulfur cycle, nitrogen cycle, and the production of oxygen via photosynthesis. Understanding the timing of the evolution and diversification of these microbes therefore permits us to more precisely infer how biological and geological processes co-evolved on Earth. With this knowledge, we can better infer the prevailing conditions of the continents, oceans, and atmospheres across deep time, reconstructing a much more rich narrative of the history of our inhabited planet. This history is key to understanding habitability in general, and is a central theme in Astrobiology research.

There are only two preserved records of events on the early earth: that preserved within rocks, and that 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 this 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 stratigraphic inference to be used to determine the relative ordering of these groups in time; similarly, these events can propagate fossil date calibrations from one branch of the Tree of Life to another.

Current ongoing projects within the lab:

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.