Graduation Year

2018

Document Type

Honors Thesis

Degree Name

Bachelor of Arts

Department

Natural Sciences

Faculty Advisor

David Crowley

Abstract

Members of halophilic archaea, like Halobacterium, are remarkably resistant to ultraviolet light (UV). However, it is unclear to what extent other halophilic archaea share this phenotype, despite the common generalization that halophilic archaea are UV resistant. Species of halophilic archaea found in salt flats at high altitude, where the atmosphere is of a lesser density than at sea level, experience an increased intensity of UV. It was hypothesized that strains of halophilic archaea that reside at a high altitude in the Salar de Uyuni in the Andes Mountain would be more UV resistant than strains isolated at sea level. Diverse genera, including Haloterrigena and Natrinema from the Andes Mountains, Haloferax from the Dead Sea, and Halobacterium, were cultured to logarithmic phase, irradiated with increasing doses of UV-C light, diluted, and plated on solid media. Spotted plates were exposed to fluorescent light or kept wrapped in foil to test the effect of photoreactivation, a light-dependent DNA repair process. We observed that (1) there was no photoreactivation in non-pigmented strains, (2) a strain of Natrinema was notably sensitive to UV, and (3) Halobacterium was the most resistant to UV. I will discuss the diversity of resistance to UV among halophilic archaea and possible cellular mechanisms associated with UV resistance.

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