Browsing by Author "Sanford, Robert A."

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Diversity and evolution of nitric oxide reduction in bacteria and archaea
(Proceedings of the National Academy of Sciences, 2024-06) Murali, Ranjani; Pace, Laura A.; Sanford, Robert A.; Ward, L. M.; Lynes, Mackenzie M.; Hatzenpichler, Roland; Lingappa, Usha F.; Fischer, Woodward W.; Gennis, Robert B.; Hemp, James
With the advent of culture-independent techniques for studying environmental microbes, our knowledge of their diversity has exploded, uncovering unique organisms, pathways, and proteins carrying out important processes in the biosphere. Novel biochemical reactions are often proposed based on sequence data, but experimental validation is difficult and rare. In this work, we used environmental sequence data to find enzymes that produce the greenhouse gas N2O from NO and validated our hypothesis with experiments. These new enzymes likely contribute to global N2O fluxes and expand the breadth of nitrogen cycling. We also demonstrated that these enzymes evolved multiple times from oxygen reductases, indicating that the evolutionary histories of aerobic respiration and denitrification—and more broadly the oxygen and nitrogen cycles—are tightly connected.
Physiology, Metabolism, and Fossilization of Hot-Spring Filamentous Microbial Mats
(2019-04) Dong, Yiran; Sanford, Robert A.; Inskeep, William P.; Srivastava, Vaibhav; Bulone, Vincent; Fields, Christopher J.; Yau, Peter M.; Sivaguru, Mayandi; Ahren, Dag; Fouke, Kyle W.; Weber, Joseph; Werth, Charles R.; Cann, Isaac K.; Keating, Kathleen M.; Khetani, Radhika S.; Hernandez, Alvaro G.; Wright, Chris; Band, Mark; Imai, Brian S.; Fried, Glenn A.; Fouke, Bruce W.
The evolutionarily ancient Aquificales bacterium Sulfurihydrogenibium spp. dominates filamentous microbial mat communities in shallow, fast-flowing, and dysoxic hot-spring drainage systems around the world. In the present study, field observations of these fettuccini-like microbial mats at Mammoth Hot Springs in Yellowstone National Park are integrated with geology, geochemistry, hydrology, microscopy, and multi-omic molecular biology analyses. Strategic sampling of living filamentous mats along with the hot-spring CaCO3 (travertine) in which they are actively being entombed and fossilized has permitted the first direct linkage of Sulfurihydrogenibium spp. physiology and metabolism with the formation of distinct travertine streamer microbial biomarkers. Results indicate that, during chemoautotrophy and CO2 carbon fixation, the 87-98% Sulfurihydrogenibium-dominated mats utilize chaperons to facilitate enzyme stability and function. High-abundance transcripts and proteins for type IV pili and extracellular polymeric substances (EPSs) are consistent with their strong mucus-rich filaments tens of centimeters long that withstand hydrodynamic shear as they become encrusted by more than 5mm of travertine per day. Their primary energy source is the oxidation of reduced sulfur (e.g., sulfide, sulfur, or thiosulfate) and the simultaneous uptake of extremely low concentrations of dissolved O2 facilitated by bd-type cytochromes. The formation of elevated travertine ridges permits the Sulfurihydrogenibium-dominated mats to create a shallow platform from which to access low levels of dissolved oxygen at the virtual exclusion of other microorganisms. These ridged travertine streamer microbial biomarkers are well preserved and create a robust fossil record of microbial physiological and metabolic activities in modern and ancient hot-spring ecosystems.