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- Creators: College of Integrative Sciences and Arts
- Creators: Stout, Valerie
Description
Pathogenic Gram-negative bacteria employ a variety of molecular mechanisms to combat host defenses. Two-component regulatory systems (TCR systems) are the most ubiquitous signal transduction systems which regulate many genes required for virulence and survival of bacteria. In this study, I analyzed different TCR systems in two clinically-relevant Gram-negative bacteria, i.e., oral pathogen Porphyromonas gingivalis and enterobacterial Escherichia coli. P. gingivalis is a major causative agent of periodontal disease as well as systemic illnesses, like cardiovascular disease. A microarray study found that the putative PorY-PorX TCR system controls the secretion and maturation of virulence factors, as well as loci involved in the PorSS secretion system, which secretes proteinases, i.e., gingipains, responsible for periodontal disease. Proteomic analysis (SILAC) was used to improve the microarray data, reverse-transcription PCR to verify the proteomic data, and primer extension assay to determine the promoter regions of specific PorX regulated loci. I was able to characterize multiple genetic loci regulated by this TCR system, many of which play an essential role in hemagglutination and host-cell adhesion, and likely contribute to virulence in this bacterium. Enteric Gram-negative bacteria must withstand many host defenses such as digestive enzymes, low pH, and antimicrobial peptides (AMPs). The CpxR-CpxA TCR system of E. coli has been extensively characterized and shown to be required for protection against AMPs. Most recently, this TCR system has been shown to up-regulate the rfe-rff operon which encodes genes involved in the production of enterobacterial common antigen (ECA), and confers protection against a variety of AMPs. In this study, I utilized primer extension and DNase I footprinting to determine how CpxR regulates the ECA operon. My findings suggest that CpxR modulates transcription by directly binding to the rfe promoter. Multiple genetic and biochemical approaches were used to demonstrate that specific TCR systems contribute to regulation of virulence factors and resistance to host defenses in P. gingivalis and E. coli, respectively. Understanding these genetic circuits provides insight into strategies for pathogenesis and resistance to host defenses in Gram negative bacterial pathogens. Finally, these data provide compelling potential molecular targets for therapeutics to treat P. gingivalis and E. coli infections.
ContributorsLeonetti, Cori (Author) / Shi, Yixin (Thesis advisor) / Stout, Valerie (Committee member) / Nickerson, Cheryl (Committee member) / Sandrin, Todd (Committee member) / Arizona State University (Publisher)
Created2013
Description
Across large areas of eastern and midwestern North America, a severe reduction in multiple populations of bat species has been observed as the result of the emerging fungal disease, white-nose syndrome (WNS). WNS is caused by a psychrophilic (i.e. cold loving) fungus, Pseudogymnoascus destructans (Pd), that invades the skin of bats during hibernation. Recent studies have shown that during hibernation, bats have decreased immune system activity which would suggest increased susceptibility to infection. Antimicrobial peptides (AMPs) are an important component of the innate immune system and are expressed constitutively within all tissues that serve as barriers against infection. Killing pathogens at the level of the skin could prevent the need for more complex immune responses likely inhibited during hibernation, and therefore AMPs could be critical in combating infection by Pd and reducing population loss of susceptible bat species. In this investigation, the fungicidal activity of commercially available AMPs derived from the skin of multiple taxa, including amphibians, catfish, and humans were compared in order to study immunity at the level of the skin. Additionally, our aim was to create optimal methods for a low-cost antimicrobial-assay protocol that would provide quantitative results. We found that killing abilities at various concentrations of dermaseptin S-1 against Ca ATCC 10231 were consistent with literature values, while our values for magainin 2 and parasin 1 were far from the values previously recorded by other studies. It is possible that some differences can be accounted for by the difference in antimicrobial assay procedures, but our findings suggest potential differences to the well-known killing abilities of certain peptides nonetheless. Overall, the protocol established for the antimicrobial assays using serial dilutions and Sabouraud Dextrose plates was successful.
ContributorsFrazier, Eric (Co-author) / Lake, Alexis M. (Co-author) / Moore, Marianne (Thesis director) / Penton, Christopher (Committee member) / College of Integrative Sciences and Arts (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
Across large areas of eastern and midwestern North America, a severe reduction in multiple populations of bat species has been observed as the result of the emerging fungal disease, white-nose syndrome (WNS). WNS is caused by a psychrophilic (i.e. cold loving) fungus, Pseudogymnoascus destructans (Pd), that invades the skin of bats during hibernation. Recent studies have shown that during hibernation, bats have decreased immune system activity which would suggest increased susceptibility to infection. Antimicrobial peptides (AMPs) are an important component of the innate immune system and are expressed constitutively within all tissues that serve as barriers against infection. Killing pathogens at the level of the skin could prevent the need for more complex immune responses likely inhibited during hibernation, and therefore AMPs could be critical in combating infection by Pd and reducing population loss of susceptible bat species. In this investigation, the fungicidal activity of commercially available AMPs derived from the skin of multiple taxa, including amphibians, catfish, and humans were compared in order to study immunity at the level of the skin. Additionally, our aim was to create optimal methods for a low-cost antimicrobial-assay protocol that would provide quantitative results. We found that killing abilities at various concentrations of dermaseptin S-1 against Ca ATCC 10231 were consistent with literature values, while our values for magainin 2 and parasin 1 were far from the values previously recorded by other studies. It is possible that some differences can be accounted for by the difference in antimicrobial assay procedures, but our findings suggest potential differences to the well-known killing abilities of certain peptides nonetheless. Overall, the protocol established for the antimicrobial assays using serial dilutions and Sabouraud Dextrose plates was successful.
ContributorsLake, Alexis (Co-author) / Frazier, Eric (Co-author) / Moore, Marianne (Thesis director) / Penton, Christopher (Committee member) / W.P. Carey School of Business (Contributor) / College of Integrative Sciences and Arts (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
White-nose syndrome (WNS) is a cutaneous fungal infection caused by Pseudogymnoascus destructans (Pd) which was first observed in the United States in 2006. Pd infects bats during hibernation and leads to the development of cutaneous lesions and behavioral changes that can result in the animal's death. This study generated the first complete bat skin proteome for the WNS resistant gray bat (Myotis grisescens) to optimize sample preparation methods and identify immune proteins that may signal resistance. Wing tissue was collected from a female gray bat and processed in a Barocycler using 4M or 8M urea followed by an in-gel trypsin digestion of pooled samples and processing of separate samples without digestion specifically to capture and identify small antimicrobial peptides. Both undigested and digested samples were analyzed using a Thermo Fisher LTQ Orbitrap Velos mass spectrometer and interpreted using PEAKS software. A total of 29 immune proteins were identified including the antimicrobial peptide dermcidin. This method will be applied to a larger range of samples from five species variably impacted by WNS to compare skin proteomes with the aim of identifying immune proteins that are responsible for resistance at the barrier where Pd invades.
ContributorsBoone, Brianna Marie (Author) / Moore, Marianne (Thesis director) / Steele, Kelly (Committee member) / College of Integrative Sciences and Arts (Contributor) / Department of Psychology (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
The study of bacterial resistance to antimicrobial peptides (AMPs) is a significant area of interest as these peptides have the potential to be developed into alternative drug therapies to combat microbial pathogens. AMPs represent a class of host-mediated factors that function to prevent microbial infection of their host and serve as a first line of defense. To date, over 1,000 AMPs of various natures have been predicted or experimentally characterized. Their potent bactericidal activities and broad-based target repertoire make them a promising next-generation pharmaceutical therapy to combat bacterial pathogens. It is important to understand the molecular mechanisms, both genetic and physiological, that bacteria employ to circumvent the bactericidal activities of AMPs. These understandings will allow researchers to overcome challenges posed with the development of new drug therapies; as well as identify, at a fundamental level, how bacteria are able to adapt and survive within varied host environments. Here, results are presented from the first reported large scale, systematic screen in which the Keio collection of ~4,000 Escherichia coli deletion mutants were challenged against physiologically significant AMPs to identify genes required for resistance. Less than 3% of the total number of genes on the E. coli chromosome was determined to contribute to bacterial resistance to at least one AMP analyzed in the screen. Further, the screen implicated a single cellular component (enterobacterial common antigen, ECA) and a single transporter system (twin-arginine transporter, Tat) as being required for resistance to each AMP class. Using antimicrobial resistance as a tool to identify novel genetic mechanisms, subsequent analyses were able to identify a two-component system, CpxR/CpxA, as a global regulator in bacterial resistance to AMPs. Multiple previously characterized CpxR/A members, as well as members found in this study, were identified in the screen. Notably, CpxR/A was found to transcriptionally regulate the gene cluster responsible for the biosynthesis of the ECA. Thus, a novel genetic mechanism was uncovered that directly correlates with a physiologically significant cellular component that appears to globally contribute to bacterial resistance to AMPs.
ContributorsWeatherspoon-Griffin, Natasha (Author) / Shi, Yixin (Thesis advisor) / Clark-Curtiss, Josephine (Committee member) / Misra, Rajeev (Committee member) / Nickerson, Cheryl (Committee member) / Stout, Valerie (Committee member) / Arizona State University (Publisher)
Created2013
Description
The United States’ War on Drugs declared in 1971 by President Richard Nixon and revamped by President Reagan in the 1980s has been an objectively failed initiative with origins based in racism and oppression. After exploring the repercussions of this endeavor for societies and individuals around the world, global researchers and policymakers have declared that the policies and institutions created to fight the battle have left devastation in their wake. Despite high economic and social costs, missed opportunities in public health and criminal justice sectors, and increasing limits on our personal freedoms, all the measures taken to eradicate drug abuse and trafficking have been unsuccessful. Not only that, but militarized police tactics, mass incarceration, and harsh penalties that stifle opportunities for rehabilitation, growth, and change disproportionately harm poor and minority communities. <br/>Because reform in U.S. drug policy is badly needed, the goals of America’s longest war need to be reevaluated, implications of the initiative reexamined, and alternative strategies reconsidered. Solutions must be propagated from a diverse spectrum of contributors and holistic understanding through scientific research, empirical evidence, innovation, public health, social wellbeing, and measurable outcomes. But before we can know where we should be headed, we need to appreciate how we got to where we are. This preliminary expository investigation will explore and outline the history of drug use and prohibition in the United States before the War on Drugs was officially declared. Through an examination of the different patterns of substance use, evolving civil tolerance of users, racially-charged anti-drug misinformation/propaganda campaigns, and increasingly restrictive drug control policies, a foundation for developing solutions and strengths-based strategies for drug reform will emerge.
ContributorsSherman, Brooke (Author) / Jimenez-Arista, Laura (Thesis director) / Mitchell, Ojmarrh (Committee member) / College of Integrative Sciences and Arts (Contributor) / Department of Psychology (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05