Ribosome Rescue is Essential in the Pathogen Francisella tularensis
Open Access
- Author:
- Goralski, Tyler
- Graduate Program:
- Biochemistry, Microbiology, and Molecular Biology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- November 14, 2018
- Committee Members:
- Kenneth Keiler, Dissertation Advisor/Co-Advisor
Girish Kirimanjeswara, Committee Chair/Co-Chair
Timothy Meredith, Committee Member
Scott Lindner, Committee Member
Sandeep Prabhu, Outside Member - Keywords:
- Francisella tularensis
ArfT
ribosome rescue - Abstract:
- The growing increase in the prevalence of drug resistant bacteria has created a massive demand for new therapeutics, capable of targeting novel pathways in bacteria. The drug resistance problem in the medical clinics is exacerbated by the looming threat of bioterror attacks with drug resistant, weaponized pathogens. The pathogen Francisella tularensis is a particular cause for concern, as it has been engineered as a bioweapon in the past. Recently, ribosome rescue has been deemed an attractive target for antibiotic development in part because factors with which it is associated are found in all bacteria, and are lacking in eukaryotic cells. The primary ribosome rescue pathway is trans-translation, but some bacteria contain one or both of the known backup systems ArfA and ArfB. The findings of this dissertation will show that ribosome rescue inhibitors have exceptional antimicrobial activity against both attenuated and fully virulent strains of F. tularensis in vitro and during ex vivo infection, with almost no cytotoxicity to host cells. However, it has been previously demonstrated that trans-translation is dispensable for viability in F. tularensis, despite not having homologs to either of the known alternative ribosome rescue factors, ArfA or ArfB. The lack of observable off-target effects with ribosome rescue inhibitors suggests that F. tularensis contains an alternative ribosome rescue pathway. The data presented in this dissertation will also show that F. tularensis contains an alternative ribosome rescue system, ArfT, which releases non-stop complexes through the recruitment of RF1 or RF2. Further characterization studies showed that lack of both ArfT and trans-translation was synthetically lethal in F. tularensis. Moreover, overexpression of ArfT in F. tularensis cells lacking trans-translation suppresses the slow growth phenotype, indicating that ArfT can act as an alternative ribosome rescue system when trans-translation is inactive. Collectively, the findings presented here suggest that ribosome rescue is essential for F. tularensis survival and that ribosome rescue inhibitors are good lead compounds for antibiotic development.