Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

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    THE ROLE OF GENOME ORGANIZATION AND FILAMENTOUS BACTERIOPHAGE ON GONOCOCCAL BIOLOGY AND PATHOGENICITY
    (2024) Kopew, Jessica; Stein, Daniel C; Cell Biology & Molecular Genetics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Gonorrhea, caused by the bacterium Neisseria gonorrhoeae (GC), represents a significant global health concern as it is the second most common bacterial STI and has a rising rate of antimicrobial resistance. The first study of this thesis aims to elucidate the causes and consequences of gonococcal genome reorganization. Here I found that when looking at many GC strains’ genomes, each GC strain had a unique genome organization including both inversions and translocation events. I also saw a consistent pattern of DNA high sequence similarity on both sides of the translocation or inversions, consistent with homologous recombination driven reorganization. PCR analysis of inversion events suggests that these large-scale reorganization events are both stable and rare. Growth curve analysis demonstrates a wide variability in growth rate between strains. Proteomic analysis suggests reorganization driven changes to replication termination location leads to upregulation of many kinds of proteins including energy metabolism and antimicrobial resistance associated genes. This study suggests that homologous recombination driven genome reorganization can have large impacts on gonococcal biology and pathogenicity. This study demonstrates the need for future gonococcal studies to use multiple GC strains from a diverse background to capture the wide variability in GC phenotypes. The second study of this thesis sought to uncover the role filamentous bacteriophage play in GC biology. I found that every GC strain currently in the NCBI database at the date of this study contains four filamentous bacteriophage gene regions in the GC genome. I found that FA1090Δfil (a GC strain lacking all four filamentous bacteriophage gene regions) grew poorly at 37⁰C both in broth and on agar, as compared to wild type FA1090. However, there was no difference when the strains were grown at 34⁰C or when grown without shaking, demonstrating the condition dependent nature of this growth advantage. FA1090Δfil formed larger bacterial aggregates than FA1090 WT. When these strains were analyzed for their ability to produce biofilms, no differences were seen in the overall biofilm’s biomass, yet the overall structure of the biofilms were different, with FA1090Δfil producing taller and rougher biofilms. Previous unpublished research in the Stein Lab demonstrates that filamentous phage derived proteins are capable of deteriorating the integrity of epithelial cell cultures and cervical tissue explants. The data from this chapter suggests that filamentous phage provide the gonococcus with a growth advantage, inhibit bacterial aggregation, alter the structure of the GC biofilm, and that phage proteins can lead to loss of the integrity of the epithelium. Taken en toto, these studies demonstrate that both alterations in bacterial genome organization and contributions from filamentous bacteriophage genomes can impact gonococcal biology and pathogenicity, which could be key to preventing and treating GC infections.
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    MOLECULAR ISOLATION OF THE MOV-1 LOCUS IN HEXAPLOID BREAD WHEAT
    (2020) Mahlandt, Alexander Robert; Tiwari, Vijay K; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Wheat provides a substantial portion of globally consumed calories, yet faces growing challenges to meet yield needs. Traits affecting floral architecture and grain number hold immense promise for increasing yield potential. Multi-ovary wheat is a unique mutant line that holds potential in improving yields, characterized by the formation of 2-3 grains per floret in a given wheat spike. Described is a multi-approach mapping effort that refines the chromosomal position of the MOV1 locus at high resolution. A radiation hybrid map, linkage map, and refined physical map are reported. Further mutation analysis recovered missense mutations within a candidate gene, displaying a quantitatively reduced phenotype. Expression profiling of the candidate gene reveals up-regulation at crucial developmental stages. Structural investigation of the gene and surrounding locus identified two insertion/deletion events that suggest a pathway for transcriptional regulation. The results presented implicate the candidate gene in the manifestation of the multi-ovary phenotype.