Date of Award
Spring 2021
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Chemistry & Biochemistry
Program/Concentration
Chemistry
Committee Director
Erin B. Purcell
Committee Member
Lesley H. Greene
Committee Member
Alvin A. Holder
Committee Member
Patrick C. Sachs
Abstract
The human pathogen Clostridioides difficile is increasingly tolerant of multiple antibiotics and causes infections with a high rate of recurrence, creating an urgent need for new preventive and therapeutic strategies. The stringent response, a universal bacterial response to extracellular stresses, governs antibiotic survival and pathogenesis in diverse organisms but has not previously been characterized in C. difficile. This dissertation explores the ability of C. difficile to mount the stringent response. The bacteria encode a full-length, canonical bifunctional Rel/Spo Homolog or RSH enzyme. C. difficile RSH is incapable of utilizing GTP as a substrate but readily synthesizes putative 5’-pGpp-3’ alarmones. Transcription of rsh is stimulated by bacterial stationary phase onset, nutrient limitation, and exposure to the antibiotics clindamycin and metronidazole. Transcriptional suppression of rsh increases bacterial antibiotic susceptibility, suggesting that RSH contributes to bacterial antibiotic tolerance and survival. Chemical inhibition of RSH by the 5’-ppGpp-3’ analog Relacin similarly increases antibiotic susceptibility in epidemic C. difficile, indicating that RSH inhibitors are a viable strategy for drug development against Clostridioides difficile infection. Finally, mechanisms contributing to C. difficile host colonization and aspects of bacterial behavior during infection remain unclear. Therefore, this dissertation also explores nutrient-derived motility regulation of the pathogen during host intestinal mucus colonization. An epidemic C. difficile strain suppresses motility in the presence of high unchained N-acetylneuraminic acid, an intestinal mucus component. The observed motility suppression is independent of bacterial tumbling but robust single species biofilm formation by R20291 and motility suppression in response to high NEU5A concentration may be regulated by the same signaling network(s).
Rights
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DOI
10.25777/05ee-2b17
ISBN
9798516056086
Recommended Citation
Pokhrel, Astha.
"Evaluating the Role of the Stringent Response Mechanism in Clostridioides difficile Survival and Pathogenesis"
(2021). Doctor of Philosophy (PhD), Dissertation, Chemistry & Biochemistry, Old Dominion University, DOI: 10.25777/05ee-2b17
https://digitalcommons.odu.edu/chemistry_etds/56
Included in
Biochemistry Commons, Chemistry Commons, Microbiology Commons