Thesis (Ph. D.)--University of Oregon, 1999. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 101-110). Also available for download via the World Wide Web; free to University of Oregon users. Address: http://wwwlib.umi.com/cr/uoregon/fullcit?p9957566.

Thesis (M.Sc.)--York University, 2005. Graduate Programme in Biology. / Typescript. Includes bibliographical references (leaves 49-54). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url%5Fver=Z39.88-2004&res%5Fdat=xri:pqdiss &rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR11779

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Thesis (Ph.D.)--University of Idaho, April 2006. / Major professor: Holly A. Wichman. Includes bibliographical references. Also available online in PDF format.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 166-178).

For my dissertation research, I used a model system of bacteria and bacteriophage to study patterns of genome evolution. I performed whole-genome sequencing of replicate populations to determine the genetic changes responsible for a repeatable pattern of coevolution between bacteria and phage. I found that genetic changes conferring resistance in bacteria negatively impacted other traits such as growth rates and sensitivity to antibiotic. Different resistance mutations varied in the magnitude of their pleiotropic costs, and this resulted in a fixation bias favoring mutations that minimized pleiotropic effects. I manipulated the environment and found that differential pleiotropy between environments drove repeatable evolution at different genetic scales. Finally, I explored theoretically how bacteria, phage, and resource interact through a dynamic system of feedbacks. I used a mathematical model to describe priority effects in evolution, where the expected fate of a beneficial mutation varies depending upon whether it appears before or after a competing mutation. / 10000-01-01

Bacteriophages are promising biosensing systems in bioactive paper application due to their specific detection of bacteria. Different chemicals including wet strength resins were used to improve paper properties. This work investigated the influence of wet strength resins (PAE and PVAm) on bacteriophage activity, and proposed another method of using Poly NIP AM microgel to separate bacteriophage from paper surface. Compared with filter paper, the cationic polymer PAE and PVAm treated paper exhibited high phage binding efficiency but low phage activity due to the electrostatic interaction. PVAm had strong phage adsorption and almost completely deactivated the phage particle. Streptavidin was coupled to PolyNIPAM microgel in the presence of EDC, and T4 bacteriophage genetically modified with biotin was immobilized to microgel particle which resulted in a 10-fold improvement in attachment when compared with T4 wild-type phage. The microgel-phage coupling efficiency was very low, there were more than 10^6 micro gel particle for every active phage. And micro gel supported phages were deactivated after coating on the PAE/PVAm treated paper. / Thesis / Master of Applied Science (MASc)

Bacteriophage Felix O1 was studied for applicability as a Salmonella intervention. Felix O1's potential as a Salmonella therapeutic was explored, as was its utility as a food application. Felix O1 is specific for and infects most serovars within the genus Salmonella. The entire 86.155-kb sequence of the phage's linear, double-stranded chromosome was determined. 213 open reading frames (ORFs) were found, including 23 homologues of phage genes (e<0.008). Homology searches do not indicate genes that would be expected to increase virulence of Salmonella. Thirteen T4 homologues were found, including rIIA and rIIB, rapid lysis genes of T-even phages. Site-directed mutagenesis of the rIIB region was attempted by homologous recombination with plasmids containing luxAB of Vibrio harveyi. No DrIIB luxAB+ recombinants resulted from the methods tried. Serial in vivo passage was used to select for a longer-circulating Felix O1 mutant using the modified methods of Merril et al., (1996). No difference was found in the clearance of wild-type (WT) and Felix O1 following nine serial passages. Injection of 10⁹pfus yielded 24-hour concentrations of 6.5 and 4.9 log10 pfus/ml plasma for WT and 9th passage, respectively. Both isolates were undetectable in plasma by 72 hours, but remained in spleens at 96 hours. A large-plaque Felix O1 variant (LP) isolated during in vivo serial passage was compared with WT for Salmonella growth suppression. Spectrophotometric measurement of BHI cultures indicated greater suppression of S. typhi by LP than by WT, a difference not seen with S. typhimurium DT104. Both isolates suppressed 24-hour S. typhimurium DT104 growth on experimentally-contaminated chicken frankfurters at 22°C. Untreated frankfurters yielded 6.81 log10 Salmonella cfus/g, whereas WT and LP-treated samples yielded 5.01 and 4.70 log10 cfus/g, respectively. Both phages suppressed the Salmonella typhimurium DT104 growth (p<0.0001), but the isolates did not perform differently (p=0.5088). Presence of Salmonella caused a higher yield of WT phage than from the uninoculated group (p=0.0011), but did not affect LP yield (p=0.4416). With Salmonella present, the 24-hour LP concentration was lower than WT concentration. This supports the surmised LP rapid-lysis phenotype since T4 rapid-lysis mutants typically exhibit lower burst sizes than wild-type phage. / Ph. D.

Bacteriophages, a promising antimicrobial alternative to modern antibiotics, can rapidly overcome bacterial resistance. However, the propagation of therapeutic phages in gram-negative bacteria leads to proinflammatory contaminants, notably endotoxins (lipopolysaccharides). To meet strict regulations on endotoxin levels, the widely accepted method for phage purification is based on polyethylene glycol precipitation followed by cesium chloride density gradient ultracentrifugation. This method, while effective, is labor-intensive and produces only small quantities of purified phage products. Moreover, the current studies on using membrane adsorbers in this application have primarily focused on removing endotoxins or recovering phages, without addressing the variability in physical properties of bacteriophages that necessitates strain-specific process development. In contrast, this thesis introduces a novel high-throughput flat sheet membrane screening approach. This approach not only aims to evaluate the effect of varying solution conditions on bacteriophage purification but also provides a comprehensive solution to the limitations of the current method, guiding larger-scale purification work. Using two clinically derived bacteriophage, this work demonstrates that the multi well device used in this work is appropriate for this application, with little background binding of bacteriophage to the device itself. Bacteriophage binding to the membrane was found to be both sensitive to the dilution of the preparation and contact time with a given membrane. The device was used to evaluate the overall binding productivity of the membranes, finding that the Natrix and Sartobind Q membranes possess superior productivity to that of Mustang Q. Furthermore, this work demonstrated that the method could be used to rapidly screen the effects of varying sodium chloride molarity on both bacteriophage and endotoxin binding, with the effect of greater NaCl molarity on both bacteriophage and endotoxin binding being generally comparable to expectations.Finally, this work demonstrates that improvements in the translatability of screened conditions to larger-scale techniques (e.g., Syringe Filtration) require a better understanding of the underlying interactions occurring between the biomolecules and membranes. / Thesis / Master of Applied Science (MASc)

Thesis (M.S.)--University of Alabama at Birmingham, 2007. / Title from first page of PDF file (viewed on June 25, 2009). Includes bibliographical references (p. 52-56).