Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Environmental Engineering and Earth Science

Committee Chair/Advisor

Dr. Nicole Martinez

Committee Member

Dr. Mark Blenner

Committee Member

Dr. Timothy DeVol

Committee Member

Dr. Cindy Lee

Committee Member

Dr. Lindsay Shuller-Nickles


The work presented herein provides quantitative data related to bacteria exposed in situ to two radionuclides relevant to nuclear sensing: plutonium-239 (239Pu) and iron-55 (55Fe). Originally motivated by the fundamental science underlying biosensing, liquid cultures of Pseudomonas putida and Escherichia coli were exposed to radionuclides over the course of 15-day experimental periods with the intent of gaining insight into the response of these bacteria. An essential component of characterizing or utilizing this response in a meaningful way is an understanding of the dose leading to that response. This dissertation narrows the knowledge gap associated with dose-response of microorganisms at environmentally relevant radionuclide concentrations through consideration of factors that influence the local dose, i.e., microdosimetry, experienced by the bacteria. These studies found that 239Pu accumulation in P. putida cells increased initially but plateaued after about 5 days, whether or not complexed with citrate. Moreover, 239Pu concentration in E. coli cells was greater than that in P. putida cells which may be the result of a stronger complexing agent made by E. coli for the purpose of Fe uptake. In cultures grown with 55Fe, over 75% of 55Fe was located in cell samples because of internal and external accumulation. When P. putida cultures were grown with 239Pu and 55Fe in combination, as well as 239Pu in combination with stable Fe, results indicate that 239Pu inhibited the uptake of 55Fe, and that the presence of Fe in cultures may promote pathways for Fe accumulation that are used by 239Pu. Finally, consideration of RNA extractions specifically suggested that 239Pu and 55Fe detected in RNA extraction samples is the result of binding to RNA prior to the time of extraction, as opposed to flow through or binding after cell lysis, and it highlights the practical importance of nucleic acid sample characterization to radiation protection, more generally. The work presented in this dissertation supports a more robust understanding of the behavior of 239Pu and 55Fe in bacteria systems and provides the groundwork necessary for the development of appropriate microdosimetric models for bacteria as well as more informed interpretation of transcriptomic analysis.

Author ORCID Identifier




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