Isolating and Characterizing an Fe(III) Transforming Deep Sea Thermophilic Archaeon



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Thermophilic bacteria and archaea that grow optimally between 50-80°C thrive in deep-sea hydrothermal vent environments. These organisms adapt and evolve unique chemosynthetic mechanisms to flourish in chemically rich vent environments in the complete absence of sunlight. This study examines one such mechanism in which microoganisms utilize Fe(III) oxides to gain energy through the metabolic process of dissimilatory iron reduction. Because the metabolism has not been studied and characterized for thermophilic bacteria and archaea, this thesis investigates the presence of such organisms in hydrothermal fluid samples collected from a diffuse vent site called Marker 113 at Axial Volcano in the northeastern Pacific Ocean. Organisms are isolated and enriched for with Fe(III) to obtain a pure isolate. Iron transformation was determined using ferrozine assays to measure Fe(II) production, and the mechanism utilized was investigated using visualization with scanning electron microscopy and transmission electron microscopy. Furthermore, the ability of the isolate to perform other metabolisms as well as grow at temperatures other than 80°C was also explored. Lastly, phylogenetic analyses were used to determine the identity of the organism and place it among other already characterized and isolated strains. The work presented in this thesis lays the foundation for studies relevant to the field of astrobiology. These organisms that thrive in high temperatures, as well as respire and transform Fe(III), perform metabolisms that are among the earliest metabolisms known for Earth. They are considered archaic in nature and serve as model organisms for extraterrestrial environments. Hydrothermal vent environments, from where the organisms in this study have been collected, are also relevant from an astrobiological perspective. It has been suggested that subsurface hydrothermal activity may have provided niches on Mars and Jupiter’s moon Europa for chemolithoautotrophic life. In the context of these hypotheses, this thesis adds to the knowledge available for microbial Fe(III) transformation in deep-sea vent systems. It makes available organisms that can contribute to future studies of biosignatures relevant to life detection missions.



Thermophile, Astrobiology, Hydrothermal Vents, Archaea, Fe(III) Reducers