Dissertation
DELETION OF A GENETIC REGION OF LP17 AFFECTS PLASMID COPY NUMBER AND GENE EXPRESSION IN BORRELIA BURGDORFERI
Washington State University
Doctor of Philosophy (PhD), Washington State University
01/2022
DOI:
https://doi.org/10.7273/000004519
Handle:
https://hdl.handle.net/2376/125015
Abstract
Borrelia burgdorferi, the Lyme disease pathogen, is maintained in its enzootic life cycle of tick and mammalian hosts through complex gene regulatory pathways encoded on its uniquely fragmented genome. This genome consists of over 20 plasmids, and the regulatory mechanisms of plasmid maintenance and replication are largely unknown. The bbd21 gene, encoded on linear plasmid 17 (lp17) and a member of the paralogous family 32 proteins, was originally proposed as a putative parA orthologue involved with plasmid partitioning; however, this function has not been confirmed to date. Because lp17 is a high-fidelity plasmid in B. burgdorferi clinical isolates with increasing evidence as a regulatory hub that modulates expression of virulence factors important for host adaptation, it is critical to elucidate the mechanisms of lp17 plasmid regulation and its link to virulence factor expression to understand disease pathogenesis and identify potential targets for Lyme disease prevention and therapeutic intervention.Chapter Two of this dissertation details the characterization of a bbd21-bbd22 deletion mutant and the impacts of this deletion on plasmid copy number and murine infectivity. Our work showed that lp17 copy number is affected by in vitro growth phase and host environment. In spirochetes lacking bbd21-bbd22, we demonstrated that lp17 copy number is altered under high-passage and mammalian-host adapted conditions. In a mouse infection model, we found that deletion of bbd21-bbd22 resulted in decreased tissue colonization, particularly the heart. Lastly, we established that bbd21 transcription appeared to be independent of direct rpoS regulation.
In Chapter Three, we present preliminary data to support the possibility that plasmid copy number may impact gene dose and have global effects on gene regulation that is important for microbial pathogenesis by B. burgdorferi. By transcriptomic analyses, bbd21-bbd22 deletion resulted in 50 differentially expressed genes from in vitro-cultivated spirochetes and 145 differentially expressed genes from mammalian host-adapted spirochetes. We show some qRT-PCR data for gene expression validation. Future studies to study the impact of gene dose and virulence factor expression are required to further elucidate this potentially novel regulatory system in the Lyme disease spirochete.
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Details
- Title
- DELETION OF A GENETIC REGION OF LP17 AFFECTS PLASMID COPY NUMBER AND GENE EXPRESSION IN BORRELIA BURGDORFERI
- Creators
- Jessica Katherine Wong
- Contributors
- Troy Bankhead (Advisor)Leigh Knodler (Committee Member)Joshua Ramsay (Committee Member)Devendra Shah (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Veterinary Medicine, College of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 88
- Identifiers
- 99900882926201842
- Language
- English
- Resource Type
- Dissertation