Graduation Year

2020

Document Type

Honors Thesis

Degree Name

Bachelor of Arts

Department

Biological and Physical Sciences

Program or Major

Biology

Faculty Advisor

David Crowley

Abstract

The goal of this project was to characterize the growth and UV resistance of four unique halophilic strains, JOR-1, BOL 4-2, BOL 6-1 and BOL 5-4. Halophilic archaea are interesting to study in part because of their notably high UV resistance. Four previously uncharacterized halophilic archaea, JOR-1, a Salararchaeum from the Dead Sea sediments, BOL 4-2, a high altitude Halorubrum from the Salar de Uyuni, and BOL 6-1 and BOL 5-4, both Natrinema from a salt mine in Bolivia, were cultured, their growth rates were measured, and their relative resistance to ultraviolet light exposure was determined. It was found that JOR-1, BOL 4-2, and BOL 6-1 had very similar doubling times (~3.5-5 hours) while BOL 5-4 grew significantly slower with a doubling time of 5.2 days. JOR-1 and BOL 4-2 each exhibited the high UV resistance typical of halophiles despite their different origins and genetic backgrounds. However, BOL 6-1 and BOL 5-4, isolated from the same location and found to be members of the same genus, showed unusual UV resistance profiles. BOL 6-1 is a relatively UV sensitive halophile while BOL 5-4, which lacks the typical halophilic red/orange pigmentation, showed a notable defect in its ability to perform photoreactivation, a key DNA repair process active only in the presence of blue light wavelengths. This work helps us better understand these four previously uncharacterized strains and adds to our understanding of the natural diversity of halophilic archaea, particularly pertaining to pigmentation and UV resistance.

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