Date of Award

2022

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Microbiology and Immunology

Abstract

Bacterial colonization of host surfaces can result in symbiotic or pathogenic associations.As bacteria becomes more resistant to antibiotics, pathogenic bacterial colonization poses an increasing risk to human health. Symbiotic associations that have beneficial outcomes for both the host and the microbe can serve as models to investigate how bacterial processes affect colonization of host surfaces. The symbiotic relationship between the Gram-negative, bioluminescent bacterium Vibrio fischeri and the Hawaiian bobtail squid is one such model (E. V. Stabb & Visick, 2013). The study of this exclusive relationship has developed in a way where in vitro phenotypes can predict the ability of the microbe to form a successful symbiotic association with the squid (E. V. Stabb & Visick, 2013). V. fischeri itself is closely related to marine organisms such as Vibrio parahaemolyticus and Vibrio vulnificus, which cause disease in humans. They all share the syp locus, a set of operons encoding glycosyltransferases, export proteins, and putative regulators involved in biofilm formation and symbiotic colonization. The fact that V. fischeri shares the loci responsible for biofilm formation with its pathogenic family members, but is non-pathogenic, makes this model organism important for initial investigations into its pathogenic family members. V. fischeri has two chromosomes with the first larger chromosome containing essential genes and the second smaller chromosome containing niche genes (Xu, Dziejman, & Mekalanos, 2003). It also has a plasmid containing a type IV secretion system along with a phage integrated into the genome. V. fischeri is highly adaptable to many environmental situations compared to other bacteria in the same genus (Ochman & Moran, 2001). Its adaptability can primarily be ix attributed to its second chromosome, which contains genes needed for specific functions necessary for its symbiotic relationships. V. fischeri can symbiotically associate with a variety of different host organisms, but since these associations are achieved through competition, different strains will have variable degrees of successful colonization with different hosts (Nishiguchi, 2002). Its best studied symbiotic association is with the Hawaiian bobtail squid or Euprymna scolopes. In this thesis, I explore the role of the transcription factor NagC in a variety of symbiosis- relevant traits, including motility, luminescence, and biofilm formation. As described below, NagC was previously shown to be required for symbiotic colonization, making it vital to understand how this protein functions. Thus, I will first describe the symbiosis and the known regulators that contribute to key stages of colonization. Then, I will describe the structure of NagC and the key functional domains necessary for its function as a transcription factor. Next, I will describe the genes NagC is known to regulate in E. coli and V. fischeri along with the metabolism of N-acetylglucosamine. Finally, I will describe new biofilm conditions discovered by Courtney N. Dial and regulation of syp-dependent biofilm formation.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.

Available for download on Wednesday, July 26, 2023

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