Doctoral Dissertations

Date of Award


Degree Type


Degree Name

Doctor of Philosophy



Major Professor

Jeremiah G. Johnson

Committee Members

Elizabeth Fozo, Chunlei Su, Jun Lin, Dan Jacobson


Campylobacter jejuni is a leading cause of bacterial-derived gastroenteritis worldwide, with a significant impact on human health. Due to the increasing prevalence of antibiotic resistant strains and the potential for post infectious disorders, identifying and characterizing colonization factors allowing C. jejuni to cause disease in susceptible hosts is of increasing importance. The work in chapter two of this dissertation addresses a previously identified colonization factor, the transcriptional regulator HeuR, by investigating the regulatory role of HeuR in methionine biosynthesis in C. jejuni. Expression of a gene in the methionine biosynthetic pathway, cystathionine beta-lyase (MetC), was significantly increased in a HeuR mutant when compared to wild-type C. jejuni, with growth and viability defects observed when a metC mutant was grown in limited media without methionine. Significant decreases in adherence, invasion into, and survival within human colonocytes were also observed for a metC mutant, indicating a role for methionine biosynthesis during infection of susceptible hosts. The work in chapter three of this dissertation uses a variety of biomolecular techniques to begin characterizing HeuR in terms of protein-DNA interactions, oligomeric state, and ligand-binding. It was determined that HeuR interacts with promoter regions identified by transcriptomic data, but with varying affinity, perhaps indicating the different regulatory roles of HeuR. Oligomeric results indicate purified HeuR exists as a dimer in solution and ligand-binding assays suggest HeuR may bind metabolic intermediates, including citrate and pyruvate. While the work described for the previous two chapters focus on the biochemical and physiological characterization of HeuR, the work in the fourth chapter of this dissertation is a surveillance study investigating the prevalence of environmental C. jejuni in the region of East Tennessee and to make genomic comparisons to C. jejuni isolated from human infections during the same time period. C. jejuni was isolated from a variety of sources, including water, cattle, and chickens and bioinformatic comparisons showed genomic similarity of human isolates with those from cattle and chickens. Taken together, the work in this dissertation demonstrates the importance of C. jejuni gene regulation in response to environmental conditions and the resulting adaptation to survive and cause disease.

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