Calorimetric measurements of heat flow and total heat production can inform on the energetics of microbial activity. Nanocalorimetry permits such investigations in environments (natural or laboratory) where energy supplies are extremely limited and/or very few cells are metabolically active. We will present nanocalorimetry data obtained during incubations of unamended formation fluids from the oceanic crust (~300 m deep at the Juan de Fuca Ridge flank) and the continental subsurface (~1500 m deep at the Sanford Underground Research Facility in South Dakota). Enthalpic responses by the resident microbial communities to addition of organic carbon, inorganic electron donors, and nutrients will also be discussed. We further used nanocalorimetry on laboratory experiments with model organisms to determine the energetics associated with carbon, electron donor, and nutrient limitations. For example, with a sulfate reducing bacterium, we quantified the significant cost during the metabolic transition from ammonium assimilation to N<sub>2</sub> fixation. In another set of experiments, with an evolving population of <i>E. coli </i>mutants that express the GASP (growth advantage in stationary phase) phenotype, we recorded distinct heat events associated with the emergence of nascent mutant populations.

Calorimetric determination of microbial activity in low-energy environments

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.