Date of Graduation

12-2018

Document Type

Thesis

Degree Name

Master of Science in Food Science (MS)

Degree Level

Graduate

Department

Food Science

Advisor

Steven C. Ricke

Committee Member

Steven Foley

Second Committee Member

Young Min Kwon

Keywords

Biofilm, Pellicle, QRT-PCR, Salmonella, Serovar

Abstract

Biofilms are communities of microorganisms associated by a matrix of extracellular polymers. In this state, microorganisms occupy an ecological niche distinct from their free-floating, planktonic counterparts. Also, biofilm bacteria become biologically unique as they form communities and lose motility. The acquisition of these physiological attributes enables the biofilm to persist through harsh environmental conditions, including antimicrobial induced stress and to resist sanitization efforts. Because of these features, biofilms can rapidly disseminate across numerous surfaces and as they establish, become challenging to remove. This is a particular issue for the food industry as processing plants offer favorable conditions for biofilm formation by providing complex surfaces composed of diverse materials that are frequently inoculated with pathogens and provide an abundance of nutrients and water. This thesis initiates investigations into the mechanisms behind biofilm formation in processing plants, and with such knowledge potentially result in novel treatments in the future. In particular, Salmonella enterica, one of the most prevalent foodborne pathogens worldwide, can produce biofilms that are difficult to remove. The thesis starts with a literature review detailing the mechanisms behind biofilm formation, evaluating the state of biofilms in food processing, and finishing with current and future mitigation strategies (Chapter 1). Next, this thesis includes four research chapters, with the first evaluating the ability of disinfectants to reduce Salmonella biofilms (Chapter 2); the second with a genome announcement about our genomic elucidation of four Salmonella strains isolated from poultry sources that are known to produce biofilms (Chapter 3); the third detailing our exploration of the pellicle forming properties of Salmonella with a focus on the lesser studied Kentucky serovar (Chapter 4); before ending with an evaluation of transcriptional dynamics of poultry isolates of different Salmonella serovars during biofilm formation (Chapter 5). Data presented herein will provide novel insight into Salmonella biofilm dynamics, mitigation, and genetics.

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