A central theme of our research is quantifying the thermodynamic potential and rates of reactions that microorganisms catalyze in natural settings and the lab. This includes direct measurement of the heat flow associated with microbial activity in nanocalorimeters as well as the application of computational models to assess Gibbs energies of biogeochemical phenomena, and in some cases, their rates. Recent nanocalorimetry experiments reveal microbial activity in deep subsurface oceanic crustal fluids and growth phase transitions, while ongoing research includes studies on nitrogen metabolism and nutrient limitation. Published research from the lab also includes Gibbs energy calculations that attempt to a) reveal heretofore undiscovered catabolisms; b) identify dominant catabolic pathways in complex natural systems; c) quantify the amount of energy required to live in different habitats and more. Finally, we have also been working to quantitatively combine energetic and rate analysis by assessing how power varies in different microbial ecosystems. We have applied this approach to marine sediments and soils and are working towards doing so on other planetary bodies.