Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Structural characterization of the Csa3/cA4 complex - a nexus for class 1 CRISPR-Cas immune response coordination & establishing a cure for highly efficient galectin expression(Montana State University - Bozeman, College of Letters & Science, 2024) Charbonneau, Alexander Anthony; Chairperson, Graduate Committee: C. Martin Lawrence; This is a manuscript style paper that includes co-authored chapters.Though Class I CRISPR-Cas systems, primarily Type I and Type III, are the most abundant CRISPR systems in archaea and bacteria, mechanisms driving their immune response regulation are not well understood. Csa3 family transcription factors, composed of N-terminal CARF and C-terminal winged helix-turn-helix domains, are frequently encoded within Type I CRISPR-Cas systems. Csa3 transcription factors are hypothesized to bind cyclic oligoadenylate (cOA) second messengers produced by Type III interference complexes, likely modulating their DNA-binding activity. Therefore, we investigated the interaction between Csa3a and cyclic tetra-adenylate (cA4). Isothermal titration microcalorimetry showed S. solfataricus Csa3a binds cA4 at biologically relevant concentrations in an entropically driven interaction. Ring nuclease assays revealed Csa3a lacks self-regulatory phosphodiesterase activity exhibited by other CARF domain proteins. We crystallized and solved the structure of the Csa3/cA4 complex, which revealed conserved motifs are responsible for cA4 binding and illuminated significant conformational changes induced by the interaction. We also identified an 18-bp palindromic motif, which we designated CAPPa, that is conserved in the 27 sequenced members of the order Sulfolobales, and shows synteny with Csa3a and acquisition genes in these genomes. We found Csa3a binds CAPPa in a nonspecific, cooperative, and cA4-independent manner. These characteristics suggest a more complex method of transcriptional regulation than previously hypothesized. However, the interaction between Csa3a and cA4 confirmed here signifies a nexus between Type I and Type III systems; we thus propose a model in which this interaction coordinates the two arms of an integrated immune system to mount a synergistic, highly orchestrated, adaptive immune response. We applied the workflow designed to produce significant protein quantities for crystallographic studies of Csa3a to the study of Homo sapiens galectin proteins, a family of beta-galactoside-binding proteins. Here, we identified a putative autoinhibitory mechanism affecting traditional IPTG-induction methods by characterizing IPTG-binding capabilities of galectins and quantifying basal protein expression over various IPTG concentrations. To bypass this predicted feedback loop, we employed a highly efficient and approachable autoinduction method, resulting in a 7-fold increase in protein expression. Much of this work was done in the context of a course-based undergraduate research experience with great success.Item Quantifying robustness of the gap gene network(Montana State University - Bozeman, College of Letters & Science, 2024) Andreas, Elizabeth Anne; Chairperson, Graduate Committee: Tomas Gedeon; Bree Cummins (co-chair)Early development of Drosophila melanogaster (fruit fly) facilitated by the gap gene network has been shown to be incredibly robust, and the same patterns emerge even when the process is seriously disrupted. We investigate this robustness using a previously developed computational framework called DSGRN (Dynamic Signatures Generated by Regulatory Networks). Our mathematical innovations include the conceptual extension of this established modeling technique to enable modeling of spatially monotone environmental effects, as well as the development of a collection of graph theoretic robustness scores for network models. This allows us to rank order the robustness of network models of cellular systems where each cell contains the same genetic network topology but operates under a parameter regime that changes continuously from cell to cell. We demonstrate the power of this method by comparing the robustness of two previously introduced network models of gap gene expression along the anterior-posterior axis of the fruit fly embryo, both to each other and to a random sample of networks with same number of nodes and edges. We observe that there is a substantial difference in robustness scores between the two models. Our biological insight is that random network topologies are in general capable of reproducing complex patterns of expression, but that using measures of robustness to rank order networks permits a large reduction in hypothesis space for highly conserved systems such as developmental networks.Item Investigating the regulation of virulence by Sae in Staphylococcus aureus(Montana State University - Bozeman, College of Agriculture, 2020) Collins, Madison Paige Martin; Chairperson, Graduate Committee: Jovanka Voyich-Kane; Ranjan K. Behera, Kyler B. Pallister, Tyler J. Evans, Owen Burroughs, Caralyn Flack, Fermin E. Guerra, Willis Pullman, Brock Cone, Jennifer G. Dankoff, Tyler K. Nygaard, Shaun R. Brinsmade and Jovanka M. Voyich were co-authors of the article, 'The accessory gene saeP of the saeR/S two-component gene regulatory system impacts Staphylococcus aureus virulence during neutrophil interaction' in the journal 'Frontiers in microbiology' which is contained within this dissertation.; Kyler Pallister and Jovanka M. Voyich were co-authors of the article, 'Differential analysis of host/pathogen RNA expression via next generation sequencing reveals Staphylococcus aureus utilizes saeR/S-mediated factors to inhibit human neutrophil functions following phagocytosis' which is contained within this dissertation.Staphylococcus aureus (S. aureus) is a common commensal bacterium known to colonize, at minimum, 30% of the human population. It is also capable of causing a range of diseases that span from minor skin- and soft-tissue infections to life-threatening diseases. The diversity of S. aureus infections is due to the ability of the bacteria to sense and respond to environmental change. Virulence regulation in S. aureus can be attributed to the use of two-component gene regulatory systems (TCS). TCS can sense a variety of encounters including: antibiotics, heat stress, or immune cell encounter. Neutrophils are a key leukocyte involved in bacterial clearance in the human host. It follows that S. aureus has evolved mechanisms to sense and respond to neutrophils. The Sae TCS, is immediately up-regulated after neutrophil phagocytosis and has been demonstrated to be critical in the success of S. aureus both in vitro and in vivo. SaeS, the histidine kinase, and the respective response regulator, SaeR, are established components of the Sae TCS and their importance during neutrophil evasion and pathogenesis is well established. However, little is known about two accessory genes, saeP and saeQ. Results described herein using human neutrophil and murine models of infection provide evidence that SaeP modulates the Sae-mediated response of S. aureus against human neutrophils and suggest that saeQ and saeP together impact pathogenesis in vivo. To identify additional host and pathogen factors important during neutrophil interaction, we used differential analysis of host/pathogen RNA expression via Next Generation Sequencing to define the influence of SaeR/S on the host-pathogen transcriptome following neutrophil phagocytosis. Results determined that in the early stages of S. aureus infection, SaeR/S-dependent factors significantly modulate neutrophil processes involved in several pathways including autophagy, TNF-alpha signaling, and NF-kappaB signaling. These results suggest S. aureus uses SaeR/S-regulated virulence factors to hijack human neutrophil function at the transcriptional level to inhibit proper killing by neutrophils and allow for S. aureus persistence within the host.Item Initiation and pathogenesis of Staphylococcus aureus Pneumonia following influenza A infection(Montana State University - Bozeman, College of Letters & Science, 2019) Borgogna, Timothy Ryan; Chairperson, Graduate Committee: Jovanka Voyich-Kane; Adrian Sanchez-Gonzalez, Kelly Gorham and Jovanka M. Voyich were co-authors of the article, 'A precise pathogen delivery and recovery system for murine models of secondary bacterial pneumonia' in the journal 'JOVE Journal of visualized experiments' which is contained within this dissertation.; Bennett Hisey, Emily Heitman, Joshua J. Obar, Nicole Meissner and Jovanka M. Voyich were co-authors of the article, 'Secondary bacterial pneumonia by Staphylococcus aureus following influenza A infection is saeR/S dependent' in the journal 'Journal of infectious diseases' which is contained within this dissertation.; Madison M. Collins, Kyle A. Glose, Kyler B. Pallister, Tyler K. Pallister and Jovanka M. Voyich were co-authors of the article, 'Uncovering the executioner: disruption of pulmonary surfactant by influenza A triggers Staphylococcus aureus Pneumonia' which is contained within this dissertation.Infection influenza A virus (IAV) leads to increased host susceptibility to secondary bacterial pneumonia. In cases such as these, Staphylococcus aureus (S. aureus) has emerged as the dominant bacterial pathogen associated with severe infection outcomes. S. aureus is a common commensal of the anterior nares and is frequently trafficked into the lower respiratory tract through inhalations, micro-aspirations, and direct mucosal dispersion. Despite recurrent exposure to the lungs and the capacity to cause severe disease, cases of S. aureus pneumonia are rare in immunocompetent hosts. Previous efforts interrogating S. aureus secondary bacterial pneumonia have largely focused on the immunomodulation that occurs during the antecedent influenza infection and have ignored the virulence contributions of the bacterial pathogen. To that end, we developed a murine model of secondary pneumonia to investigate S. aureus pathogenesis following influenza A infection. We identify that secondary bacterial pneumonia by S. aureus is dependent on the activation of the two-component regulatory system (TCS) SaeR/S. Further, studies demonstrated that in the absence of IAV infection the healthy lung environment suppresses virulence gene expression. Characterization of the lung environment revealed that the lipid constituents of pulmonary surfactant suppress S. aureus virulence production. Our data provide a model of secondary bacterial pneumonia wherein infection with IAV significantly reduces surfactant lipid concentrations within the lungs. The reduction of pulmonary surfactant lipids leads to a loss of S. aureus virulence suppression and rapid activation of the major virulence regulator saeR/S. Taken together, these data provide a strong rational for the low incidence of primary S. aureus pneumonia and the increased severity of S. aureus pneumonia following antecedent influenza A infection. Furthermore, these data highlight possible pulmonary surfactant replacement therapies that may significantly alleviate secondary bacterial pneumonia morbidity and mortality.Item Disruption of neutrophil reactive oxygen species production by Staphylococcus aureus(Montana State University - Bozeman, College of Letters & Science, 2018) Guerra, Fermin Ernesto; Chairperson, Graduate Committee: Jovanka Voyich-Kane; Timothy R. Borgogna, Delisha M. Patel, Eli W. Sward and Jovanka M. Voyich were co-authors of the article, 'Epic immune battles of history: neutrophils vs. Staphylococcus aureus' in the journal 'Frontiers in Cellular and Infection Microbiology' which is contained within this dissertation.; Conrad B. Addisson, Nienke W. M. de Jong, Joseph Azzolino, Kyler B. Pallister, Jos (A. G.) van Strijp and Jovanka M. Voyich were co-authors of the article, 'Staphylococcus aureus SaeR/S-regulated factors reduce human neutrophil reactive oxygen species production' in the journal 'Journal of Leukocyte Biology' which is contained within this dissertation.; Kyler B. Pallister, Tyler K. Nygaard, Mark T. Quinn, and Jovanka M. Voyich were co-authors of the article, 'Staphylococcus aureus leukocidins modulate human neutrophil reactive oxygen species production' which is contained within this dissertation.Staphylococcus aureus (S. aureus) is a bacterial pathogen that causes a wide range of human disease, from skin infections to invasive endocarditis. Neutrophils are the most abundant white blood cell in the human body, and the first line of defense following S. aureus infection. Even though neutrophils are equipped with an arsenal of bactericidal mechanisms, S. aureus survives neutrophil encounter. The mechanisms used by S. aureus to survive neutrophil killing remain unresolved. Previous studies have shown that the S. aureus SaeR/S two-component gene regulatory system is essential to survive neutrophil killing. Herein, we tested the hypothesis that S. aureus uses SaeR/S-dependent mechanisms to reduce neutrophil bactericidal mechanisms. First, we determined that S. aureus uses genes under the regulation of SaeR/S to inhibit neutrophil reactive oxygen species (ROS) production independent of previously defined mechanisms. Subsequently, we helped characterize a novel S. aureus SaeR/S-regulated virulence factor that inhibits human myeloperoxidase (MPO) activity to prevent formation of the highly bactericidal agent hypochlorous acid. Thus, S. aureus SaeR/S-regulated factors disrupt the neutrophil bactericidal mechanism with most efficacy against it, which is killing by oxidative mechanisms. We then focused on the role of S. aureus SaeR/S-regulated secreted leukocidins on neutrophil ROS production. While S. aureus leukocidins show redundancy inducing neutrophil pore formation, we determined that the surface receptors engaged by leukocidins induce distinct signaling pathways leading to ROS production. We showed that specific kinases are required for the differential production of neutrophil ROS induced by the S. aureus leukocidins LukGH and Panton-Valentine leukocidin (PVL). Importantly, the signaling pathways induced by S. aureus leukocidins through neutrophil surface receptors differ from the signals induced by physiological ligands through the same surface receptors. These results suggest S. aureus leukocidins 'shortcircuit' neutrophil signals to induce aberrant ROS production. In conclusion, S. aureus SaeR/S-regulated factors prevent proper bacterial clearance by disrupting neutrophil ROS production. These data provide us with a better understanding of the specific mechanisms used by S. aureus to survive neutrophil killing leading to pathogenesis.Item The role of SaeR/S in secondary Staphylococcus aureus Pneumonia(Montana State University - Bozeman, College of Agriculture, 2016) Hisey, Bennett Stephen; Chairperson, Graduate Committee: Jovanka Voyich-Kane; Timothy R Borgogna, Kyler B. Pallister, Eli W. Sward, Fermin E. Guerra and Jovanka M Voyich were co-authors of the article, 'The role of SaeR/S in secondary Staphylococcus aureus pneumonia' submitted to the journal 'Journal of infectious diseases' which is contained within this thesis.Methicillin?resistant Staphylococcus aureus (MRSA) is a Gram?positive pathogen capable of causing diverse disease in humans. MRSA precisely controls virulence factor expression via the SaeR/S two?component gene regulatory system. While much is known about SaeR/S regulation patterns during skin infection, less is understood about the role it plays in the pulmonary environment during secondary staphylococcal pneumonia. Using an isogenic deletion mutant in pulsed field gel electrophoresis type USA300 (strain LAC) of the saeR/S two?component gene regulatory system we examined its role in mouse models of pathogenesis involving primary infection with influenza strain A/WSN/33 followed by USA300 infection. Results demonstrate SaeR/S contributes significantly to mortality during pneumonia following influenza A infection. Reverse transcription PCR and QuantiGene 2.0 assays revealed differences in both transcription of components of SaeR/S as well as virulence factors under SaeR/S control. Primary Influenza infection was seen to up regulate expression of virulence factors under control due to antecedent influenza A infection. These data underscore the importance of pathogen contribution to the pathogenesis of secondary pneumonia.Item Introducing the ArsR regulated arsenic stimulon(Montana State University - Bozeman, College of Agriculture, 2017) Saley, Tara Carolyne; Chairperson, Graduate Committee: Timothy McDermottThe United States EPA ranks arsenic as the number one environmental toxin. Since microorganisms are significant drivers of arsenic toxicity and mobility in nature, it is important to understand how microbes detect and react to arsenic. The microbial arsenic resistance operon (ars) is critical for sensing arsenic in the environment and controlling the cellular response to this toxin. The ars operon is minimally comprised of arsRBC, which codes for an ArsR transcriptional repressor, arsenite effluxer, and an arsenate reductase, respectively, with the operon negatively regulated by the transcriptional repressor, ArsR. Our model organism Agrobacterium tumefaciens 5A carries two ars operons, with each containing two arsR genes. We conducted an RNASeq study to examine the regulatory roles of the encoded four ArsR regulatory proteins as a function of +/- arsenite. We report that the regulatory influence of the ArsR proteins extends well beyond the ars operon, with both activation and repression effects. In addition to the expected arsenic resistance response, many cellular functions were impacted, including: phosphate acquisition/metabolism, sugar transport, chemotaxis, copper tolerance, and iron homeostasis. Each of the ArsR proteins uniquely influenced different sets of genes and an arsR regulatory hierarchy was observed, wherein ArsR1 is auto regulatory and negatively regulates arsR4, ArsR4 activates arsR2, and ArsR2 negatively regulates arsR3. ArsR3 is the least active with respect to number of genes regulated. To summarize, this study provides a more complete understanding of how microbial gene expression and biogeochemical cycling may be influenced by arsenic in the environment.Item Profile matrix analyzer : clustering microarray data(Montana State University - Bozeman, College of Engineering, 2001) Taubman, Julie LynnItem Gene regulation in the lac operon(Montana State University - Bozeman, College of Letters & Science, 2009) Patterson, Kathryn Grace; Chairperson, Graduate Committee: Tomas GedeonThe lac operon, a jointly controlled series of genes in the bacteria E. coli, has been studied extensively since the 1940's. The lac operon genes are transcribed and then translated into proteins necessary for transport and digestion of lactose. The operon is activated in the presence of lactose after glucose, the preferred carbon source, has been expended. In this thesis, we introduce a biophysical model using the Shea-Ackers framework for modeling promoter dynamics. The model spans two scales: the inputs are biophysical parameters of molecular interactions and the result is a level of gene expression - a macroscopic behavior of the cell. We include all experimentally suggested control mechanisms into the model, even though the experimental evidence is stronger for some of these mechanisms than others. We compare our model to experimental data and explore the individual contribution of the proposed mechanisms by removing them one by one and testing the reduced model's fit to the data. Finally, we find a minimal model which faithfully represents the available data, yet includes only the minimal number of control mechanisms.