Hamann, Bree2013-05-072013-05-072013-03https://hdl.handle.net/11299/148775University of Minnesota Ph.D. dissertation. March 2013. Major: Biochemistry, Molecular Bio, and Biophysics. Advisor: Arkady Khodursky, Ph.D. 1 computer file (PDF); x, 185 pages, appendix p. 179-185.Antibiotic resistance is one of the world's most pressing public health problems. An international survey published in 2000 measured the prevalence of antimicrobial resistance to commonly prescribed antibiotics, and found that E. coli had developed resistance of between 15-30% to ampicillin and Bactrim©, two of the most commonly prescribed antibiotics (Kahlmeter, 2002). Methotrexate, 5-fluorouracil, and Bactrim© are commonly prescribed antibiotics and cancer treatment therapies which are thought to work by a phenomenon known as thymine-less death. These treatments have been so effective in both bacteria and mammals, in part, because they target the fastest growing cells within the human body killing off cancer and bacterial infections. However, as is the case for all antibiotics eventually, their efficacy is waning. While finding new targets and therapeutic molecules is important in combating multi-resistant microorganisms and cancers, there is no guarantee that such new treatments will be any less toxic to the human host, nor more effective against their targets than what current antibiologicals used to show. Understanding the effects of thymine deprivation on the cell may open new avenues for drug targeting that will bypass current means of survival by the infectious cells resulting in maintaining use of the currently FDA-approved treatments in conjunction with new drug therapies. In this thesis I discuss work analyzing the mechanism of killing of two types of antibiotics. One is a type II topoisomerase inhibitor, simocyclinone D8, which affects supercoiling of the circular bacterial chromosome. My work described in chapter 1 show that gram negative bacteria are susceptible to the drug when their drug-efflux capacity is compromised via a knock-out of the AcrB efflux pump. Chapters 2 through 5 describe published and unpublished work concerning the mechanism of thymineless death, phenomenon purported to be the mechanism of action for such commonly prescribed drugs as 5-fluoro-2-deoxyuridine, trimethoprim, methotrexate, and other anti-folate drugs.en-USThesis or Dissertation