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11. Energetically Informed Niche Models of Hydrogenotrophs Detected in Sediments of Serpentinized Fluids of the Samail Ophiolite of Oman

Author

Howells, Alta E. G., primary, Leong, James A. M., additional, Ely, Tucker, additional, Santana, Michelle, additional, Robinson, Kirt, additional, Esquivel‐Elizondo, Sofia, additional, Cox, Alysia, additional, Poret‐Peterson, Amisha, additional, Krajmalnik‐Brown, Rosa, additional, and Shock, Everett L., additional

Published
2022
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14. Marine mineral-catalyzed NO and N2O formation on the anoxic early Earth

Author

Buessecker, Steffen, Ely, Tucker, Hu, Renyu, Cadillo-Quiroz, Hinsby, Imanaka, Hiroshi, and Romaniello, Stephen

Subjects
bepress|Physical Sciences and Mathematics, bepress|Physical Sciences and Mathematics|Earth Sciences, bepress|Physical Sciences and Mathematics|Earth Sciences|Geochemistry, EarthArXiv|Physical Sciences and Mathematics|Earth Sciences|Geochemistry, EarthArXiv|Physical Sciences and Mathematics|Earth Sciences, equipment and supplies, EarthArXiv|Physical Sciences and Mathematics
Abstract

Microbial metabolisms were limited by available terminal electron acceptors in the anoxic environment of the early Archean. However, iron mineral phases in Fe2+-rich (ferruginous) oceans could have catalyzed reactions with abiotically fixed nitrogen leading to the formation of nitrous oxide (N2O), a potentially favorable terminal electron acceptor. We experimentally simulated anoxic surface-catalyzed reduction of nitrite and nitrate via green rust and magnetite. Besides N2O, we detected and quantified the formation of substantial amounts of nitric oxide (NO). While N2O escaped into the gas phase (63% of nitrite-nitrogen, with green rust as catalyst), NO remained associated with precipitates (7% of nitrite-nitrogen). Using diffusion and photochemical modeling, we show that marine N2O emissions could have sustained atmospheric N2O pools of 1-7 ppb. Although this concentration was insufficient to cause significant warming, the seawater enriched in N2O and NO could have critically affected early benthic life by providing the opportunity to conserve energy.

Published
2020

18. Spectroscopy and Viability of Bacillus subtilis Spores after Ultraviolet Irradiation: Implications for the Detection of Potential Bacterial Life on Europa.

Author

Noell, Aaron C., Ely, Tucker, Bolser, Diana K., Darrach, Halley, Hodyss, Robert, Johnson, Paul V., Hein, Jeffrey D., and Ponce, Adrian

Subjects
*EUROPA (Satellite), *BACTERIAL spores, *PHOTOCHEMISTRY experiments, *BACILLUS subtilis biotechnology, *GENETIC markers, *ASTROBIOLOGY
Abstract

One of the most habitable environments in the Solar System outside of Earth may exist underneath the ice on Europa. In the near future, our best chance to look for chemical signatures of a habitable environment (or life itself) will likely be at the inhospitable icy surface. Therefore, it is important to understand the ability of organic signatures of life and life itself to persist under simulated europan surface conditions. Toward that end, this work examined the UV photolysis of Bacillus subtilis spores and their chemical marker dipicolinic acid (DPA) at temperatures and pressures relevant to Europa. In addition, inactivation curves for the spores at 100 K, 100 K covered in one micron of ice, and 298 K were measured to determine the probability for spore survival at the surface. Fourier transform infrared spectra of irradiated DPA showed a loss of carboxyl groups to CO2 as expected but unexpectedly showed significant opening of the heterocyclic ring, even for wavelengths >200 nm. Both DPA and B. subtilis spores showed identical unknown spectral bands of photoproducts after irradiation, further highlighting the importance of DPA in the photochemistry of spores. Spore survival was enhanced at 100 K by ∼5× relative to 298 K, but 99.9% of spores were still inactivated after the equivalent of ∼25 h of exposure on the europan surface. Key Words: Bacillus subtilis-DPA-Viability-Icy worlds-Europa. Astrobiology 15, 20-31. [ABSTRACT FROM AUTHOR]

Published
2015
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