PhD (Doctor of Philosophy)
Date of Award
Committee Chair or Co-Chairs
David Hurley, Bert Lampson, Alok Agrawal, Antonio Rusinol
Pseudomonas aeruginosa is a Gram-negative bacillus able to colonize a wide variety of environments. In the human host, P. aeruginosa can establish an acute infection or persist and create a chronic infection. P. aeruginosa is able to establish a niche and persist in human hosts by using a wide array of virulence factors used for: movement, killing host cells, and evading immune cells and antibiotics. Understanding virulence factors and their regulation has proved to be an important means of combating the morbidity and mortality of P. aeruginosa as well as the ever-increasing threat of drug resistance. By targeting virulence factors or their regulators with antivirulence compounds, the bacterium is rendered defenseless and more readily cleared by the immune system. In this study, we examine three different contributors to virulence factor regulation. First, we examined the role of the extracellular sigma factor AlgU and its contribution to regulating a post-transcriptional RsmA. AlgU is most commonly active in chronic infecting strains that produce copious amounts of the virulence factor, alginate. We confirmed that not only was their more RsmA in this background, but that there was a previously unidentified promoter for rsmA regulated by AlgU. In concert with this study, we followed up by studying the effects of AlgR on this unknown promoter. AlgU and AlgR are known to work together, specifically on the alginate operon, and we hypothesized based off of bioinformatics data this was the case with RsmA. Second, due to increased RsmA in this chronic infection strain, we set out to identify potential unknown virulence targets of RsmA. A previously unrevealed target, pasP, was shown to directly interact with RsmA. Third, in an acute infection model strain we identified a new regulatory loop involving the two-component system AlgZ/R. In a pilW strain deficient in the motility virulence factor type IV pili, we showed increased levels of AlgZ/R compared to wildtype, PAO1. The pilW strain produced less pyocyanin, rhamnolipid, and elastase and was attenuated in J774a.1 macrophages. Overall, these studies push the understanding of virulence factor regulation and open the door to potential therapeutic targets in treating P. aeruginosa infections.
Dissertation - Open Access
Stacey, Sean, "Virulence Regulation in Pseudomonas aeruginosa via the Alginate Regulators, AlgU and AlgR, the posttranscriptional regulator, RsmA, and the Two-component System, AlgZ/R" (2018). Electronic Theses and Dissertations. Paper 3486. https://dc.etsu.edu/etd/3486
Copyright by the authors.