ORCID
https://orcid.org/0000-0003-4854-1626
Date of Award
11-9-2023
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
Bacterial pathogens commonly encounter hostile conditions, including disinfectants, antimicrobials, and the host immune system. To be successful, they must adapt through dynamic and complex regulatory mechanisms, such as post-transcriptional modifications on a variety of molecules, including tRNA. In recent years, this tRNA “epitranscriptome” has been increasingly appreciated as an under-researched mechanism for bacterial stress responses. These modifications can impact the translation efficiency of a cohort of stress response factors whose transcripts are enriched for the corresponding codons. However, the variety and roles of tRNA modification enzymes in human pathogens is still largely unknown. The Gram-negative pathogen Acinetobacter baumannii is currently acquiring multi-drug resistance at alarming rates. A. baumannii is also incredibly capable of surviving a wide range of stressors, to the extent that our understanding of its pathogenesis relies on its ability to “persist and resist,” rather than being reliant on one particular toxin or virulence factor. As tRNA modifications have not been previously characterized in A. baumannii, we hypothesized that modulating the tRNA epitranscriptome could provide A. baumannii with an array of tools to fine-tune - and potentially even completely reprogram - its stress responses. In this thesis, we assessed the roles of putative tRNA methyltransferases in the pathogenesis of A. baumannii clinical isolates. We found that the m7G methyltransferase TrmB plays a critical, niche-specific role in A. baumannii infections. Loss of trmB increased the susceptibility of multiple clinical isolates to oxidative and pH stresses. Accordingly, ΔtrmB mutants had a replication defect within macrophages and were attenuated in catheter-associated urinary tract infection and acute pneumonia murine models. Proteomic and qRT-PCR analyses revealed that loss of trmB interfered with A. baumannii’s post-transcriptional upregulation of a crucial siderophore cluster, acinetobactin, under oxidative stress. Finally, we also examined several other putative tRNA methyltransferases under oxidative, pH, osmotic, and antibiotic stresses. We found that the impact of each tRNA methyltransferase in A. baumannii is strain-specific and their impact on the strain’s virulence potential is likely dependent on A. baumannii‘s large, plastic, accessory genome. Despite this strain-dependence, these tRNA methyltransferases appear to be critical for the stress responses and pathogenesis of multiple clinical isolates. Therefore, the studies presented in this thesis demonstrate that targeting the A. baumannii tRNA epitranscriptome may be a viable strategy for therapeutic development, providing tools to combat the pathogen’s meteoric rise in multi drug resistance.
Language
English (en)
Chair and Committee
Mario Feldman
Recommended Citation
McGuffey, Jenna, "tRNA Methyltransferases Mediate Acinetobacter baumannii Pathobiology" (2023). Arts & Sciences Electronic Theses and Dissertations. 3187.
https://openscholarship.wustl.edu/art_sci_etds/3187