Date of Graduation

5-2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Cell & Molecular Biology (PhD)

Degree Level

Graduate

Department

Biological Sciences

Advisor

Young Min Kwon

Committee Member

Steven C. Ricke

Second Committee Member

Charles Rosenkrans, Jr.

Third Committee Member

Dan J. Donoghue

Abstract

Non-typhoidal Salmonella species have been major foodborne zoonotic pathogens causing serious problems in public health and food industry for several decades. Numerous Salmonella species have frequently been associated with different food commodities mainly poultry meat, eggs, and their products. This dissertation begins with a literature reviews discussing many aspects of Salmonella generally; and subsequently focused on two serotypes, Salmonella Enteritidis and S. Typhimurium as they are at the top of all other serovars responsible for most illness cases and outbreaks. In addition, some Salmonella strains have exhibited their ability to tolerate and survive many food processing treatments. We can divide this dissertation into two major sections. The first section is focused on S. Enteritidis. Since this serovar is the most foodborne routinely isolated from eggs and its products, we aimed to compare the ability of some strains in invading ovarian follicles of laying hens as a route of contaminating eggs (Chapter 2). As an important step in identifying gene function using high-throughput screening, we developed a mutant library of S. Enteritidis strain selected from the previous chapter using transposon mutagenesis (Chapter 3). This library will be a source for numerous future research projects to identify essential genes for survival and virulence in S. Enteritidis serving as potential targets to develop advance technology in controlling Salmonella. In the second section, mutants of S. Typhimurium were utilized to better understand its ability to grow in temperatures associated with human and poultry body temperatures in comparison to their wild type strain through phenotype microarray screening. In addition, we tested the same mutants in surviving some heat treatments practically applied in food processing systems (Chapter 4). In the last part (Chapter 5), a mutant library of S. Typhimurium was screened using Tn-seq technique to identify conditionally essential genes for surviving cold temperature on chicken carcass. All chapters of this dissertation including Literature Reviews (Chapter 1) have been written in journal formats to which they have been published or in preparation to be submitted.

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