Turner, Raymond JosephMonych, Nadia Karen2019-09-162019-09-162019-09-11Monych, N. K. (2019). Examining the interactions between Pseudomonas aeruginosa and Staphylococcus aureus and their effect on antimicrobial susceptibility (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.http://hdl.handle.net/1880/110940The purpose of this work was to examine the role of biomolecules involved in interspecies interactions changing antimicrobial tolerance, particularly for metals. In this thesis it was determined that compounds from P. aeruginosa were able to alter the tolerance of S. aureus to metal antimicrobials, antiseptics and antibiotics. S. aureus tolerance to Ga(NO3)3, CdSO4 and ZnSO4, the anionic metal(loids) K2TeO3, Na2SeO3 and NaAsO2 as well as tetracycline, nalidixic acid, benzalkonium chloride and hydrogen peroxide were all diminished when exposed to P. aeruginosa spent media. Conversely, P. aeruginosa spent media was able to enhance S. aureus tolerance to NiSO4, CuSO4 and AgNO3. The phenotype was dependent on growing in simulated wound fluid (SWF). When spent media was produced in either LB or a minimal media M9 with casamino acids, no difference in tolerance was provided and instead anti-Staphylococcal compounds were produced. The provided copper and silver tolerance enhancement was found to be multifactorial with both unique and similar contributors for each metal. Copper tolerance is provided by reducing its bioavailability in the media. This is performed by binding to amino acids and dihydroaeruginoate (Dha), an intermediate in the synthesis of the siderophore pyochelin. Changes to the membrane of S. aureus due to inhibition of the agr system by 3-oxo-C12-HSL likely reduces the import of copper and thus its toxicity. Production of outer membrane vesicles (OMVs) induced by the Pseudomonas Quinolone Signal (PQS) contributes to reduced silver toxicity for S. aureus. The compounds contained within OMVs, including PQS, would likely bind silver reducing its bioavailability. Amino acid catabolism of serine and threonine also increases silver tolerance in S. aureus. This likely occurs through reducing the interaction of silver with L-serine dehydratase, a necessary enzyme in conversion of threonine and serine conversion to pyruvate.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.metalantimicrobialPseudomonasstaphylococcusinterspeciesinteractionsMicrobiologyBiochemistrymaster thesishttp://dx.doi.org/10.11575/PRISM/37005