Title page for ETD etd-08182009-040256
|Type of Document
||Arrage, Andrew Anthony
||Characterization of DNA-repair potential in deep subsurface bacteria challenged by UV light, hydrogen peroxide, and gamma radiation
||Master of Science
|Benoit, Robert E.
|Falkinham, Joseph O. III
|Krieg, Noel R.
|Palumbo, A. V.
|Phelps, Tomm J.
|Date of Defense
Subsurface bacterial isolates obtained through the DOE
Subsurface Science Program were tested for resistance to UV light, gamma radiation and H202. Some deep subsurface bacteria
were resistant to UV light, demonstrating ≥1.0% survival at
fluences which resulted in a 0.0001% survival level of E. coli B. The percentage of UV resistant aerobic subsurface bacteria
and surface soil bacteria were similar; 30.8% and 25.8%
respectively. All of the microaerophilic subsurface isolates
were UV sensitive as defined in this work; however,
subsurface isolates demonstrated UV resistance levels similar
to reference bacterial strains of the same Gram reaction.
These results were not in agreement with the hypothesis that
the resistance of an organism to UV is correlated with the
amount of solar radiation in its natural habitat. Evidence
for photoreactivation and the presence of an SOS-like
mechanism was also detected in subsurface bacteria. The
presence of UV resistance and photoreactivation in subsurface
bacteria that have been shielded from solar radiation for
millions of years may point to a limited rate of evolution in
the deep subsurface environment.
In subsurface bacteria, there was a relatedness between
UV resistance and resistance to gamma radiation and H202 UV-resistant
aerobic subsurface isolates were also gamma and H202-
resistant compared to the microaerophilic isolates tested.
Due to the similarities of bacterial responses to UV, H202 , and
gamma radiation, either UV or H202 may be utilized to model the
effects of ionizing radiation on bacterial cultures used for
the bioremediation of organic and radioactive waste-containing
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