Molecular Microbiology and Immunology electronic theses and dissertations (MU)
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The items in this collection are the theses and dissertations written by students of the Department of Molecular Microbiology and Immunology. Some items may be viewed only by members of the University of Missouri System and/or University of Missouri-Columbia. Click on one of the browse buttons above for a complete listing of the works.
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Item Associating population-level variability of the gut microbiome with host phenotypes(University of Missouri--Columbia, 2024) McAdams, Zachary Lynn; Ericsson, AaronThe gut microbiome (GM) affects host growth and development, behavior, and disease susceptibility. Biomedical research investigating the mechanisms by which the GM influences host phenotypes often involves collecting fecal samples from laboratory mice. Many environmental factors can affect the composition of the GM in mice, and while efforts are made to minimize this variation, biological and technical variability exists and may influence microbiome outcomes. Here we employed a hierarchical fecal sampling strategy to 1) quantify the effect size of biological and technical variation and 2) provide practical guidance for the development of microbiome studies involving laboratory mice. We found that while biological and technical sources of variation contribute significant variability to microbiome alpha and beta diversity outcomes, their effect size is 3- to 30-times lower than that of the experimental variable in the context of an experimental group with high intergroup variability. After quantifying variability of alpha diversity metrics at the technical and biological levels, we simulated whether sequencing multiple fecal samples from individual mice improves effect size in a two-group experimental design. Collecting five fecal samples per mouse increased effect size achieving the maximum 5 percent reduction in the required number of animals per group. While reducing the number of animals required, sequencing costs were dramatically increased. Our data suggest that the effect size of biological and technical factors may contribute appreciable variability to an experimental paradigm with relatively low mean differences. Additionally, repeated sampling improves statistical power, however, its application is likely impractical given the increased sequencing costs. Autism spectrum disorders (ASD) are complex human neurodiversities increasing in prevalence within the human population. In search of therapeutics to improve quality-of-life for ASD patients, the gut microbiome (GM) has become a promising target as a growing body of work supports roles for the complex community of microorganisms in influencing host behavior via the gut-brain-axis. However, whether naturally-occurring microbial diversity within the host GM affects these behaviors is often overlooked. Here we applied a model of population-level differences in the GM to a classic ASD model - the BTBR T+ Itpr3tf/J mouse - to assess how complex GMs affect host behavior. Leveraging the naturally occurring differences between supplier-origin GMs, our data demonstrate that differing, complex GMs selectively effect host ASD-related behavior - especially neonatal ultrasonic communication - and reveal a male-specific effect on behavior not typically observed in this strain. We then identified that the body weight of BTBR mice is influenced by the postnatal GM which was potentially mediated by microbiome-dependent effects on energy harvest in the gut. These data provide insight into how variability within the GM affects host behavior and growth, thereby emphasizing the need to incorporate microbial diversity within the host GM as an experimental factor in biomedical research. Horses and other equids are reliant on the gut microbiome for health, and studies have reported associations between certain clinical conditions and features of the fecal microbiome. However, research to date on the equine fecal microbiome has often relied on small sample sizes collected from single and relatively localized geographic regions. Previous work largely employs single timepoint analyses, or horses selected based on limited health criteria. To address these issues and expand our understanding of the core microbiome in health, and the changes associated with adverse outcomes, the Equine Gut Group (EGG) has collected and performed 16S rRNA sequencing on 2,362 fecal samples from 1,190 healthy and affected horses. Here we present the EGG database and demonstrate its utility in characterizing the equine microbiome in health and acute gastrointestinal disease. The EGG 16S rRNA database is a valuable resource to study the equine microbiome and its role in equine health.Item Effects of Helicobacter pylori infection and pan-caspase inhibition on human neutrophil fate and function(University of Missouri--Columbia, 2024) Khuu, Lisa; Allen, Lee-AnnNeutrophils (polymorphonuclear leukocytes, PMN) are the first responders of the immune system and comprise up to 70 percent of circulating leukocytes in humans. Helicobacter pylori is a gastric pathogen infecting over 50 percent of people globally that causes gastritis, peptic ulcers, and gastric cancer. Uniquely, H. pylori is capable of infecting PMN, and we have shown infection induces an N1-like subtype differentiation in PMN notable for profound nuclear hypersegmentation and an extended cell lifespan. This dissertation aimed to elucidate the fate of H. pylori infected PMN. We found a stark disappearance of RIP kinases, indicating that in addition to apoptosis, infected PMN subvert necroptosis and PANoptosis death pathways. Herein, we show that H. pylori infected PMN die by an atypical pyroptosis, characterized by activated pro-inflammatory caspase-4 but not caspase-1 or caspase-5. Distinctly, Gasdermin D is not activated and accordingly, infected cells do not secrete IL-1[beta] or IL-18. Moreover, infection robustly upregulates and activates the pore forming protein ninjurin-1. Given the role of caspases in cell death, we also sought to determine the extent to which neutrophil function and lifespan are affected by treatment with the pan-caspase inhibitor Q-VD-OPh (QVD). We found that QVD-treated PMN lived five times longer than untreated cells while sustaining critical effector functions. Combined, this work advances our understanding of human neutrophil plasticity and neutrophil biology.Item Advancements in influenza glycobiology : impacts in influenza a virus evolution, fitness, and vaccine development(University of Missouri--Columbia, 2024) Alcala, Esmeralda; Wan, Xiu-Feng HenryThe Alphainfluenzavirus influenzae (FLUAV), is an enveloped, negative sense, single stranded RNA virus and part of the Orthomyxoviridae family. The FLUAV is comprised of eight genome segments, with segments HA and NA being the primary targets for host humoral responses and determining the subtypes of the influenza viruses. N-linked glycosylation may occur at the N-X-S/T sequon sites of NA and HA, and potentially impact the structure of HA and NA and thus transmissibility, antigenicity, and/or immunology of the FLUAV. FLUAVs circulating in humans have shown an increase of N-linked glycosylation sites, compared to those circulating in avian. Monitoring the heterogenicity and site occupancy of N-linked glycosylation is important in understanding the national history of FLUAVs. Advancements in glycomics technology and methods have helped precisely characterize N-linked glycosylation and develop therapeutic targets and broadly protective vaccines for influenza prevention and control.Item Deciphering the complexity of IGHMBP2 mutations : respiratory deficits as prognostic indicators of lifespan(University of Missouri--Columbia, 2024) Ricardez Hernandez, Sara Maria; Lorson, Christian L.According to the National Institutes of Health (NIH), over 10,000 rare diseases have been identified, impacting approximately 1 in 10 individuals, totaling around 30 million people in the United States. Nearly 90 percent of neuromuscular diseases (NMDs) fall under the category of rare diseases. Despite their low prevalence, NMDs are collectively common conditions. NMDs encompass a diverse range of neurological disorders, constituting a significant contributor to mortality and lifelong disability in both children and adults. NMDs include 5q-spinal muscular atrophy (SMA), spinal muscular atrophy with respiratory distress type 1 (SMARD1), and Charcot Marie Tooth Type 2S (CMT2S). SMA is a motor neuron disease caused by autosomal recessive mutations in the survival motor neuron gene 1 (SMN1) [1]. SMA is one of the most common genetic causes of infant mortality, with an incidence of 1:10,000 [2]. Progressive muscle weakness begins proximally and develops distally with the initial sparing of the diaphragm. As the disease progresses, intercostal muscles become weak, leading to thoracoabdominal asynchrony, a bell-shaped chest, and, eventually, respiratory failure [3]. In contrast, mutations in the immunoglobulin µ-DNA binding protein 2 human gene (IGHMBP2) gene on Chromosome 11q13 give rise to two different autosomal recessive diseases, SMARD1 and CMT2S. The first cases of SMARD1 were described in 1974 [4]. However, these putative SMARD1 cases were thought to be unusual presentations of an unknown etiology causing the most acute type of SMA, Werdnig Hoffman disease (SMA type 1). SMARD1 is a devastating disease: patients present with respiratory distress 1-2 months after birth due to bilateral diaphragmatic weakness and eventration, while xiv progressive distal to proximal muscle defects were not apparent until 3-4 months of age [4]. Conversely, the milder axonal neuropathy, CMT2S, was not described until 2014, after exome sequencing of two English female patients diagnosed previously with CMT2 but with no identified mutation [5]. In this work, we characterize a novel model for CMT2S, Ighmbp2H922Y/H922Y, and the first compound heterozygous model of SMARD1, Ighmbp2D564N/H922Y. Our studies delve into the intricate role of IGHMBP2 in the pathogenesis of SMARD1 and CMT2S, revealing significant differences between mouse models with homozygous recessive and compound heterozygous mutations. The H922Y homozygous mice exhibited a normal lifespan and did not display respiratory deficiencies. Mild motor function defects emerged later in life, consistent with CMT2S disease progression. Notably, lifespan cohorts in D564N/H922Y mice exhibited three distinct groups, contrasting with H922Y homozygous mice, which showed no reduction in lifespan. A groundbreaking aspect of the research is the identification of early respiratory pathology as a critical predictor of lifespan within the D564N/H922Y survival cohorts, independent of limb pathology. Moreover, this study uniquely separates IGHMBP2 function in respiration from limb motor function, underscoring the significant improvement in lifespan and fitness by reducing respiratory deficits. The findings establish a direct correlation between IGHMBP2 biochemical activity and disease pathogenesis associated with patient mutations in humans and mice, advancing our understanding of IGHMBP2 function and its impact on disease progression.Item Studies on some morphological variants of Bacillus stearothermophilus strain NCA 1518 and on two of its thermophilic bacteriophages(University of Missouri--Columbia., 1971) Humbert, Robert Dale; Fields, M. L."The remarkable heat resistance of the spores of Bacillus stearothermophilus has attracted a great deal of interest and investigation. This microorganism is of great theoretical interest because its spores represent one of the extreme parameters for the survival of living systems. The heat resistance of the spores is of practical significance because of the spoilage potential which this microorganism represents in canned foods. The spoilage produced by B. stearothermophilus is known as "flat sour" spoilage because the microorganism produces acid but no gas when it grows in canned foods. The acid and other products of the organism cause a sour flavor and an unplesant odor. The absence of gas production leaves the can flat, as opposed to the bulged or swelled condition brought about by gas production. A number of investigations showed that the heat resistance of the spores of B. strearothermophilus varies widely. Heat resistance of spores varied with the ccmposition of the medium on which the spores were produced, the temperature at which they were produced, the medium in which they were heated, the particular strain involved, and the variant type within the strain. The National Canners Association (NCA) strain 1518 of B. stearothermophilus is widely used for determinations of heat resistance. A wide variety of F values was reported in the literature. Some of these differences may be attributed to the existence of variant types within the stocks of B. stearothermophilus NCA 1518. Some of these variants, identified as Rough (R) and Smooth (s), according to their colonial morphology, were found by Fields (1963), to differ in the thermal resistance of their spores. The differences in heat resistance and the composition and reaction of these variants to a number of different selective pressures were investigated by Fields and his co-workers. Since there are spontaneous morphological mutations in microbial populations, and since there are observed differences in the heat resistance and biochemistry of the known morphological variants of B. stearothermophilus RCA. 1518, an investigation of the specific interrelationships involved with morphological mutations was desirable. The study also could help in understanding the variations in heat resistance as well as perhaps providing a little more insight into the extreme thermophilic and thermoduric nature of B. stearothermophilus. Some phases of its genetics were also explored. The approach used in this investigation was to isolate a series of rough and smooth (morphological) mutants from the rough and smooth stocks of B. stearothermophilus NCA 1518. The mutant stocks were evaluated for heat resistance of the spores and biochemical capabilities of the vegetative cells as compared to the "standard" rough and smooth strains. Studies of the relationship between hosts and their parasites often have provided valuable information regarding the host itself as well as the host-parasite system. For that reason, this research effort included some investigations into bacteriophages which parasitize B. stearotheimophilus NGA 1518. It was hoped that this might possibly lead to the development of transduction as an investigational tool available for the study of the genetics of this species."--Introduction.