| dc.description.abstract | Vibrio parahaemolyticus is the leading cause of seafood-borne gastroenteritis in humans following the consumption of contaminated seafood, and is a consequential organism for aquaculture and human health. To generate disease, the pandemic strain of V. parahaemolyticus encodes toxins and hemolysins, two type III secretion systems, and two type VI secretion systems. Primarily, two type III secretion systems, T3SS-1 and T3SS-2, drive rapid host-cell cytotoxicity and enterotoxicity, respectively. How V. parahaemolyticus uses these secretion systems to coordinate virulence is not understood. It is clear that T3SS-1 is expressed in calcium-depleted, magnesium-supplemented rich media. However, it is not clear how this signal is transduced into the cell, or through what mechanism the expression of the T3SS-1 master regulator ExsA is induced. Using a transposon mutagenesis screen, we identified HlyU, a SmtB/ArsR family transcriptional regulator as essential for exsA expression. Next, we explored the mechanism of HlyU-dependent expression of exsA, and identified a non-β-DNA superstructure – a DNA cruciform – involved in the regulation of exsA. Through a currently unknown mechanism, HlyU and the cruciform structure appear to interact to de-repress exsA expression. Taken together, these studies contribute to our understanding of exsA expression, and T3SS coordination, in V. parahaemolyticus. In addition to virulence, Vibrio spp., including V. parahaemolyticus, catabolize and assimilate chitin in the environment. Importantly, many Vibrio spp. interactions with seafood and aquacultural organisms are driven by their ability to sense, move towards, and degrade this robust carbon and nitrogen source. To better understand the connection between their environmental life and their pathogenic one, I characterized two important sugar catabolism regulators, and their role in cellular functions including chitinase secretion, biofilm formation, and T3SS-1 expression. Following, I employed a transposon-sequencing approach, which combines high-efficiency transposon mutagenesis with high-throughput DNA sequencing, to explore the genes necessary for chitin catabolism genome-wide. Here, I identified uncharacterized sugar transport and transcriptional regulator genes as essential for growth on chitin. Vibrio spp. are a growing global burden. Understanding both how they survive in the environment, and how they coordinate virulence, is vital to predicting and managing emerging disease. | en_US |
