Date of Award
7-2-2024
Degree Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Microbiology and Immunology
First Advisor
Andrew Ulijasz
Abstract
The toxic dialdehyde glyoxal is found in all domains of life and results as a by-product from a variety of metabolic activities such as DNA oxidation, lipid peroxidation, and autoxidation of sugars such as glucose. If allowed to accumulate, the reactive aldehyde groups of glyoxal have the ability to react with a plethora of molecules including, DNA, lipids, and protein side chains. Most notably, glyoxal can react with arginine, lysine, and cysteine residues, forming irreversible covalent modifications known as advanced glycation end products (AGEs). These glyoxal-derived AGEs can impair protein function, leading to cellular toxicity and eventual cell death. Due to this, detoxification of glyoxal is necessary to prevent cellular damage, and many systems have evolved to remediate its accumulation and toxic effects. However, the transcriptional and molecular responses to glyoxal have remained severely understudied, especially in prokaryotic systems. Herein, we describe the transcriptional response of the nosocomial bacterial pathogen Pseudomonas aeruginosa to glyoxal. Exposure of P. aeruginosa to subinhibitory concentrations of glyoxal resulted in a sulfur and phosphate starvation response, and surprisingly the upregulation of virulence determinants. The most upregulated GO-responsive gene was an antibiotic monooxygenase (ABM) domain, renamed here aldehyde-responsive quorum-sensing inhibitor (ArqI). An ArqI atomic structure revealed a novel hexamer wheel harboring a glyoxal-arginine post-translational modification. Upon expression by GO exposure, ArqI migrates to a single pole, which is dependent on its hexameric quaternary structure. ArqI was found to shut down biosynthesis of the critical quorum-sensing molecule PQS, which controls expression of many virulence factors, by forming a complex with PqsA; the first enzyme in PQS biosynthesis. In line with this, we found that ArqI is required for full virulence in a murine sepsis model. In addition, this work has discovered the first known transcription factor that directly senses and responds to glyoxal to mediate this response, as well as designed and characterized a genetic tool for transcriptional and translational reporters in P. aeruginosa and other Gram-negatives. Our work here defines the first global microbial response to GO and suggests that host GO could be a novel inducer of P. aeruginosa virulence. Although, the mechanism by which the host exposes P. aeruginosa to glyoxal remains enigmatic. Taken together, these data highlight the need for further investigation into the role of aldehydes at the host-pathogen interface.
Recommended Citation
Corcoran, Christopher James, "Characterization of the Glyoxal Response in Pseudomonas Aeruginosa" (2024). Dissertations. 4097.
https://ecommons.luc.edu/luc_diss/4097
