A central theme of my research is quantifying the thermodynamic potential and rates of reactions that microorganisms catalyze in natural settings and the lab. By doing so, the basic variables that govern natural phenomena, temperature, pressure and composition, are used to do decipher the limits to life. Highlights of my work on this topic include:

•  using reaction energetics to discover new metabolisms;

• developing and applying reaction transport models to quantify the rates and spatial distribution of different microbial catabolisms in global marine sediments; 

• developing new mathematical models for low-energy microbial ecosystems that incorporate how variable physiological states correspond with the demand for energy;

• working with many others to combine geochemical data, bioenergetic calculations, nanocalorimetry and DNA sequencing to reveal likely metabolic pathways operating in marine and terrestrial subsurface environments; and  

• developing new theoretical tools to relate thermodynamic potential to rates of microbial metabolisms.