Barrett

Barrett, The Honors College at Arizona State University proudly showcases the work of undergraduate honors students by sharing this collection exclusively with the ASU community.

Barrett accepts high performing, academically engaged undergraduate students and works with them in collaboration with all of the other academic units at Arizona State University. All Barrett students complete a thesis or creative project which is an opportunity to explore an intellectual interest and produce an original piece of scholarly research. The thesis or creative project is supervised and defended in front of a faculty committee. Students are able to engage with professors who are nationally recognized in their fields and committed to working with honors students. Completing a Barrett thesis or creative project is an opportunity for undergraduate honors students to contribute to the ASU academic community in a meaningful way.

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The impact of Staphylococcus aureus volatiles on Pseudomonas aeruginosa phenotypes

Description
Persons with cystic fibrosis (CF) are highly susceptible to lung infections caused by the opportunistic pathogens Pseudomonas aeruginosa (PA) and Staphylococcus aureus (SA). By age 20, ~16% of CF patients have co-infections with these two bacteria, and this number grows as the patients age1. PA-SA co-infections are associated with worsened…

Persons with cystic fibrosis (CF) are highly susceptible to lung infections caused by the opportunistic pathogens Pseudomonas aeruginosa (PA) and Staphylococcus aureus (SA). By age 20, ~16% of CF patients have co-infections with these two bacteria, and this number grows as the patients age1. PA-SA co-infections are associated with worsened clinical outcomes in CF patients, but the reasons are not well understood. One hypothesis is that SA influences the production of PA virulence factors and other chronic infection phenotypes. Previous work in our lab investigated the effects of SA on PA quorum-regulated phenotypes when they are grown as planktonic co-cultures. We are expanding on this result by testing whether SA can influence PA phenotypes without being in direct contact, and without being able to exchange soluble secreted factors. In this study, we hypothesized that SA produces volatile organic compounds (VOCs) that cause changes in PA phenotypes leading to a down-regulation of motility and protease production, and increased antibiotic resistance. To test this hypothesis, we exposed two laboratory strains of PA to the VOCs produced by pre-grown lawns of two strains of SA, and measured PA motility by conducting swarming, swimming, and twitching assays, measuring protease production, as well as antibiotic sensitivity. After exposing PA to a pre-grown lawn of SA, there was a significant difference in some phenotypes compared to controls. There were significant decreases in swarming motility, twitching motility, and protease production, and an increase in a bright green pigment (possibly siderophores) when PA was exposed to SA. The degree of phenotypic alterations was dependent on both the PA strain and the SA strain being tested. Exposure to SA VOCs also altered PA sensitivity to ciprofloxacin, though one strain caused an increase in susceptibility while the other SA strain caused an increase in resistance. These data demonstrate that SA VOCs can influence PA phenotypes in vitro, which may have relevance for CF patients who are co-infected with these two bacteria.
ContributorsLopez, Brianna Marie (Author) / Bean, Heather (Thesis director) / Misra, Rajeev (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
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Investigating the Role of the Las and Rhl Quorum Sensing Systems in the Pathogenesis of Pseudomonas aeruginosa

Description
Pseudomonas aeruginosa is an opportunistic bacterial pathogen commonly associated with increased morbidity and mortality in cystic fibrosis (CF) patients. To adapt to the CF lung environment, P. aeruginosa undergoes multiple genetic changes as it moves from an acute to a chronic infection. The resultant phenotypes have been associated with chronic…

Pseudomonas aeruginosa is an opportunistic bacterial pathogen commonly associated with increased morbidity and mortality in cystic fibrosis (CF) patients. To adapt to the CF lung environment, P. aeruginosa undergoes multiple genetic changes as it moves from an acute to a chronic infection. The resultant phenotypes have been associated with chronic infection and can provide important information to track the patient’s individualized disease progression. This study examines the link between the accumulation of QS genetic mutations and phenotypic expression in P. aeruginosa laboratory strains and clinical isolates. We utilized several plate-based and colorimetric assays to quantify the production of pyocyanin, rhamnolipids, and protease from paired clinical early- and late-stage chronic infection isolates across 16 patients. Exoproduct production of each isolate was compared to the mean production of pooled isolates to classify high producing (QS-sufficient) and low producing (QS-deficient) isolates. We found that over time P. aeruginosa isolates exhibit a reduction in QS-related phenotypes during chronic infections. Future research of the QS regulatory networks will identify whether reversion of genotype will result in corresponding phenotypic changes in QS-deficient chronic infection isolates.
ContributorsKaranjia, Ava Vispi (Author) / Bean, Heather (Thesis director) / Haydel, Shelley (Committee member) / Davis, Trenton (Committee member) / School of Life Sciences (Contributor) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05