Keywords

Clostridioides difficile, selenium, puupehenone, auranofin, proline, purine

Abstract

Clostridioides difficile is a bacterial pathogen that causes pseudomembranous colitis and the majority of antibiotic-associated diarrheal cases. Broad-spectrum antibiotic usage disrupts the normal gut microbiota and thereby compromises colonization resistance, the main defense against C. difficile infection. Treatment options are limited to vancomycin, fidaxomicin, and the fecal microbiota transplant. Addressing the scarcity of these therapeutics, we documented two explorations in C. difficile drug discovery: (i) evaluation of antibacterial and toxin-suppressing activity of (+)-puupehenone and similar derivatives, and (ii) clarification of a discrepancy in the hypothesized mechanism of auranofin against C. difficile. A better understanding of how C. difficile colonizes and thrives in the gut can greatly benefit therapeutic development. Interestingly, C. difficile can scavenge nutrients such as amino acids and possibly even purines during infection. Amino acids including proline and glycine act as substrates for Stickland metabolism, a bioenergetics scheme that partially relies on enzymes containing selenium in the form of selenocysteine (e.g., D-proline reductase and glycine reductase). Purines such as xanthine and uric acid can be degraded by bacterial molybdenum hydroxylases harboring an uncharacterized form of selenium, though the role of these enzymes in C. difficile physiology is poorly understood. Selenium likely plays a key role in the scavenging of these nutrients during C. difficile infection. Our investigation of these selenium-dependent enzymes revealed two new findings in C. difficile biology: (i) a link between proline-dependent growth and D-proline reductase, characterized as an energy "addiction," and (ii) a previously uncharacterized selenium-dependent pathway involved in the catabolism of xanthine and uric acid. Overall, these physiological analyses of C. difficile provide promising candidates for therapeutics and key information regarding the organism's nutrient preferences.

Completion Date

2024

Semester

Spring

Committee Chair

Self, William

Degree

Doctor of Philosophy (Ph.D.)

College

College of Medicine

Department

Burnett School of Biomedical Sciences

Degree Program

Biomedical Sciences

Format

application/pdf

Identifier

DP0028323

URL

https://purls.library.ucf.edu/go/DP0028323

Language

English

Rights

In copyright

Release Date

May 2024

Length of Campus-only Access

None

Access Status

Doctoral Dissertation (Open Access)

Campus Location

Orlando (Main) Campus

Accessibility Status

Meets minimum standards for ETDs/HUTs

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