Calorimetric measurement of energy and nutrient stimulation of microorganisms from the continental deep subsurface.

Microbial activity in the deep continental subsurface is difficult to measure due to low cell densities, low energy fluxes, cryptic elemental cycles and enigmatic metabolisms. Nonetheless, direct access to rare sample sites and sensitive laboratory measurements can be used to better understand the variables that govern microbial life underground. In this study, we sampled fluids from six boreholes at depths ranging from 244 m to 1,478 m below ground at the Sanford Underground Research Facility (SURF), a former goldmine in South Dakota, United States.

Comparative proteomics of a versatile, marine, iron-oxidizing chemolithoautotroph.

This study conducted a comparative proteomic analysis to identify potential genetic markers for the biological function of chemolithoautotrophic iron oxidation in the marine bacterium Ghiorsea bivora. To date, this is the only characterized species in the class Zetaproteobacteria that is not an obligate iron-oxidizer, providing a unique opportunity to investigate differential protein expression to identify key genes involved in iron-oxidation at circumneutral pH. Over 1000 proteins were identified under both iron- and hydrogen-oxidizing conditions, with differentially expressed proteins found in both treatments.

Sulfur disproportionating microbial communities in a dynamic, microoxic-sulfidic karst system.

Biogeochemical sulfur cycling in sulfidic karst systems is largely driven by abiotic and biological sulfide oxidation, but the fate of elemental sulfur (S ) that accumulates in these systems is not well understood. The Frasassi Cave system (Italy) is intersected by a sulfidic aquifer that mixes with small quantities of oxygen-rich meteoric water, creating Proterozoic-like conditions and supporting a prolific ecosystem driven by sulfur-based chemolithoautotrophy. To better understand the cycling of S in this environment, we examined the geochemistry and microbiology of sediments underlying widespread sulfide-oxidizing mats dominated by Beggiatoa.