Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (p. 84-109).

Thesis (M.S.)--Michigan State University. Dept. of Biochemistry and Molecular Biology, 2008. / "Advisor, Todd A. Ciche"--Acknowledgements. Title from PDF t.p. (viewed on Aug. 5, 2009) Includes bibliographical references. Also issued in print.

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Symbioses between microbes and multicellular eukaryotes are found in all biomes, and encompass a spectrum of symbiotic lifestyles that includes parasitism and disease, commensalism, and mutually beneficial interdependent host-microbe relationships. Regardless of outcome, these symbiotic lifestyles are governed by a complex molecular "courtship" between microbe and potential host. This courtship is the primary determinant of the host range of a given microsymbiont. Host immunity poses a formidable barrier to the establishment of host-microbe relationships, and the majority of microbial suitors will be thwarted by it. Only by successfully "wooing" the host cell's immune defenses with the appropriate molecular signals can a microsymbiont successfully colonize its host. A strategy common to microsymbionts across the spectrum of symbiotic lifestyles and host organisms is the delivery of microbial-encoded effector proteins into the cytoplasm of host cells to manipulate the host cell's molecular machinery for the purposes of subverting host immunity. Bacteria, in particular, have adapted a number of secretion systems for this purpose. The most well-characterized of these is the type III secretion system (T3SS), a molecular apparatus that specializes in injecting type III effector (T3Es) proteins directly into host cells. The work in this thesis focuses on T3Es of plant-associated bacteria, with particular emphasis on mutualistic bacteria. We present evidence that collections of T3Es from Sinorhizobium fredii and Bradyrhizobium japonicum are, in stark contrast to those of phytopathogenic bacteria, in a co-evolutionary equilibrium with their hosts. This equilibrium is characterized by highly conserved T3E collections consisting of many "core" T3Es with little variation in nucleotide sequence. The T3Es of Mesorhizobium loti MAFF303099 suggest a completely different picture of the evolution of T3Es. MAFF303099 recently acquired its T3SS locus, and the work in this thesis provides an evolutionary snapshot of a mutualist that is innovating a T3E collection primarily through horizontal gene transfer. Collectively, this work represents the first comprehensive catalog of T3Es of rhizobia and, in the case of Sinorhizobium and Bradyrhizobium, the first evidence of purifying selection for T3Es. / Graduation date: 2012

Indiana University-Purdue University Indianapolis (IUPUI) / Borrelia burgdorferi, a bacterium which causes Lyme disease, is maintained in nature through a cycle involving two distinct hosts: a tick vector and a mammalian host. To adapt to these two diverse environments, B. burgdorferi undergoes dramatic alterations in its surface lipoprotein. Two essential lipoproteins, outer surface protein A (OspA) and outer surface protein C (OspC), are reciprocally regulated throughout the B. burgdorferi lifecycle. Very little is known about the regulation of OspA. These studies elucidate the regulatory mechanisms controlling the expression of OspA. Various truncations of the ospA promoter were created and then studied in our novel in vitro model of ospA repression or grown within the host-adapted model. A T-Rich region of the ospA promoter was determined to be a cis-element essential for both the full expression and full repression of ospA.