Award Date
August 2024
Degree Type
Thesis
Degree Name
Master of Science (MS)
Department
Life Sciences
First Committee Member
Brian Hedlund
Second Committee Member
Henry Sun
Third Committee Member
Nicole Pietrasiak
Fourth Committee Member
Janice Pluth
Number of Pages
95
Abstract
An important question in astrobiology is whether life can exist under the levels of UVC radiation found on Archean Earth, Mars, and exoplanets. We investigated this question by studying the UVC survival of colonial cyanobacterium and lichens that grow in harsh desert environments and possess natural sunscreens. We irradiated them nonstop in a desiccated state with a UVC flux closely representing the upper limit on those planets: 55-60 W/m². After irradiation, we rehydrated and assessed their survival using chlorophyll fluorometry and by counting the number of viable colonies that formed on agar plates. All three study organisms survived two to three months of UVC exposure. Additionally, two of the study organisms, colonial cyanobacterium and cyanolichen, were irradiated for nine days under metabolically active conditions (hydrated and under visible light) to UVC fluxes found on Archean Earth. The hydrated exposure resulted in a significant decline in photosynthetic activity in the colonial cyanobacterium after just one day; however, the cyanolichen showed no reduction in activity throughout the nine-day experiment. These survival results under both dry and wet irradiation, combined with further experiments to understand the source of UVC injury to lichens, suggest that surviving under high UVC fluxes may not be an issue for life. Future work studying the growth and reproduction potential of these organisms could suggest that the surface of Mars and exoplanets are not necessarily uninhabitable just because they are exposed to UVC radiation.
Keywords
Astrobiology; Exoplanets; Extremophiles; Mars; Photobiology; Radiation Resistance
Disciplines
Biology | Environmental Sciences | Microbiology | Terrestrial and Aquatic Ecology
Degree Grantor
University of Nevada, Las Vegas
Language
English
Repository Citation
Singh, Tejinder, "UVC and Planetary Habitability: Insights from Desert Lichens and Cyanobacteria" (2024). UNLV Theses, Dissertations, Professional Papers, and Capstones. 5149.
https://digitalscholarship.unlv.edu/thesesdissertations/5149
Rights
IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/
Included in
Biology Commons, Environmental Sciences Commons, Microbiology Commons, Terrestrial and Aquatic Ecology Commons