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Description
The viscous lung mucus of cystic fibrosis (CF) patients is characterized by oxygen gradients, which creates a unique niche for bacterial growth. Pseudomonas aeruginosa and Staphylococcus aureus, two predominant microorganisms chronically infecting the airways of CF patients, typically localize in hypoxic regions of the mucus. While interspecies interactions between P. aeruginosa and S. aureus have been reported, little is known about the role of low oxygen in regulating these interactions. Studying interspecies interactions in CF lung disease is important as evidence suggests that microbial community composition governs disease progression. In this study, P. aeruginosa lab strain PAO1 and two primary clinical isolates from hypoxic tissues were cultured alone, or in combination, with methicillin resistant S. aureus (MRSA) strain N315 under hypoxic or normoxic conditions. Herein, it is shown for the first time that low oxygen conditions relevant to the CF lung affect the competitive behavior between P. aeruginosa and S. aureus. Specifically, S. aureus was able to better survive competition in hypoxic versus normoxic conditions. Competition data from different oxygen concentrations were consistent using PAO1 and clinical isolates even though differences in the level of competition were observed. PAO1 strains carrying mutations in virulence factors known to contribute to S. aureus competition (pyocyanin/phzS, elastase/lasA and lasI quorum sensing/lasI) were used to determine which genes play a role in the differential growth inhibition. The lasA and lasI mutants competed less effectively with S. aureus regardless of the oxygen level present in the culture compared to the isogenic wild type strain. These results are consistent with previous findings that elastase and lasI quorum sensing play a role in competitive behavior of P. aeruginosa and S. aureus. Interestingly, the phzS mutant competed less effectively in hypoxic conditions suggesting that pyocyanin may be important in microaerophilic conditions. This study demonstrates that oxygen plays a role in competition between P. aeruginosa and S. aureus and contributes to understanding CF environmental factors that may regulate microbial community dynamics important for disease progression with potential for development of therapeutic avenues.
ContributorsLedesma Barrera, Maria Alexandra (Author) / Nickerson, Cheryl A. (Thesis advisor) / Reyes del Valle, Jorge (Committee member) / Clark-Curtiss, Josephine (Committee member) / Stout, Valerie (Committee member) / Ott, C M (Committee member) / Arizona State University (Publisher)
Created2014
Description
In competitive Taekwondo, Electronic Body Protectors (EBPs) are used to register hits made by players during sparring. EBPs are comprised of three main components: chest guard, foot sock, and headgear. This equipment interacts with each other through the use of magnets, electric sensors, transmitters, and a receiver. The receiver is connected to a computer programmed with software to process signals from the transmitter and determine whether or not a competitor scored a point. The current design of EBPs, however, have numerous shortcomings, including sensing false positives, failing to register hits, costing too much, and relying on human judgment. This thesis will thoroughly delineate the operation of the current EBPs used and discuss research performed in order to eliminate these weaknesses.
ContributorsSpell, Valerie Anne (Author) / Kozicki, Michael (Thesis director) / Kitchen, Jennifer (Committee member) / Electrical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
The traditional action-response perspective has largely ignored the role of language in competitive dynamics. In this study, I treat language (i.e., word response) as an alternative way to react to rivals when a firm is attacked, in addition to no reaction and action-based reaction. Word response is a specific and public announcement of a focal firm’s potential move in reaction to a competitor’s word or action attack. To explore the underlying mechanism behind word responses, I aim to answer two major questions. The first question is under what situations are responders motivated to use words as competitive responses? For this question I emphasize characteristics of the action, the market, and the actor, using measures such as action type, market dependence of the responder, multimarket contact of the responder in the market, and the competitive aggressiveness of the actor. The second question is what kinds of responders are more likely to use words as competitive responses? For this question, I focus on responder characteristics, such as firm reputation, CEO tenure, and CEO duality. According to Porter’s competitive signaling theory, I argue that responders can use words in reaction to an attack in order to test the waters, deter rivalry, and demonstrate toughness because word responses require few resources, can be accomplished quickly, are reversible, while at the same time still carrying some commitment. Besides incorporating language into the action-response perspective, my dissertation also further integrates the upper-echelons perspective with competitive dynamics research, providing a more realistic and complete understanding of competitive engagement. I test my theory in the consumer electronics (CE) industry with 20 major global CE manufacturers between 2007 and 2014.
ContributorsGao, He (Author) / Cannella, Albert A. (Thesis advisor) / Yu, Tieying (Committee member) / Mesquita, Luiz (Committee member) / Arizona State University (Publisher)
Created2016