Intrinsic silver resistance of Pseudomonas aeruginosa in simulated human wound fluid

Ostaszewski, Alexandra

Intrinsic silver resistance of Pseudomonas aeruginosa in simulated human wound fluid

dc.contributor.advisor	Harrison, Joe J.
dc.contributor.author	Ostaszewski, Alexandra
dc.contributor.committeemember	Schryvers, Anthony Bernard
dc.contributor.committeemember	Storey, Douglas G.
dc.contributor.committeemember	Turner, Raymond Joseph
dc.date	2020-11
dc.date.accessioned	2020-10-22T14:13:08Z
dc.date.available	2020-10-22T14:13:08Z
dc.date.issued	2020-10-19
dc.description.abstract	A meta-analysis of randomized clinical trials using silver suggests that it does not improve patient outcomes and that the opportunistic pathogen Pseudomonas aeruginosa can persist in wounds treated with silver-impregnated bandages. However, little is known about how this microorganism withstands silver toxicity. Using strand-specific RNA-sequencing of burn-wound isolated P. aeruginosa in tandem with susceptibility testing of transposon mutants in simulated human wound fluid, we identified 46 differentially expressed genes that are bona fide silver resistance determinants. We focused on the most highly differentially expressed gene identified in the screen, copZ2. This gene is a paralog of P. aeruginosa copZ1, which encodes a copper-binding chaperone protein. CopZ2 is a small protein (65 amino acids, 6.9 kDa) that contains a M-X-C-X-H-C metal-binding motif that is essential for its function. Although CopZ1 is a putative cytoplasmic protein regulated by the copper-responsive regulator, CueR, we provide evidence that CopZ2 is enriched in the outer membrane of P. aeruginosa and that its transcription is regulated by both the putative envelope stress-response regulator, CpxR, and CueR. Purified CopZ2 binds to silver (Ag+) with an equilibrium dissociation constant (Kd) of 7.7 µM, providing it with higher affinity for silver ions than copper ions (Cu2+, Kd = 37.0 µM) in the same milieu. CopZ2 orthologues are widely distributed in Pseudomonas species, and heterologous expression of these genes confers silver tolerance to Escherichia coli. Taken together, these data begin to define the determinants of P. aeruginosa intrinsic silver resistance in environments with complex organics, and identify that CopZ2 is an evolutionarily conserved, membrane-associated, silver-binding protein that may account for a widespread ability of Pseudomonads to withstand silver toxicity.	en_US
dc.identifier.citation	Ostaszewski, A. (2020). Intrinsic silver resistance of Pseudomonas aeruginosa in simulated human wound fluid (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.	en_US
dc.identifier.doi	http://dx.doi.org/10.11575/PRISM/38344
dc.identifier.uri	http://hdl.handle.net/1880/112703
dc.language.iso	eng	en_US
dc.publisher.faculty	Science	en_US
dc.publisher.institution	University of Calgary	en
dc.rights	University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.	en_US
dc.subject	Silver tolerance	en_US
dc.subject	Pseudomonas aeruginosa	en_US
dc.subject.classification	Microbiology	en_US
dc.subject.classification	Biology--Molecular	en_US
dc.title	Intrinsic silver resistance of Pseudomonas aeruginosa in simulated human wound fluid	en_US
dc.type	doctoral thesis	en_US
thesis.degree.discipline	Biological Sciences	en_US
thesis.degree.grantor	University of Calgary	en_US
thesis.degree.name	Doctor of Philosophy (PhD)	en_US
ucalgary.item.requestcopy	true	en_US