Author ORCID Identifier

0000-0001-7248-6351

Defense Date

2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Microbiology & Immunology

First Advisor

Dr. Kimberly K Jefferson

Second Advisor

Dr. Dayanjan S Wijesinghe

Third Advisor

Dr. Phillip B Hylemon

Fourth Advisor

Dr. Martin Mangino

Fifth Advisor

Dr. Daniel Conrad

Abstract

Staphylococcus aureus produces an arsenal of virulence factors and is adept at colonizing multiple hosts by employing specific processes to persist at different sites of infection. Infections caused by this pathogen range from self-limiting infections of the skin like folliculitis to life threatening and chronic conditions like infective endocarditis, non-healing diabetic foot ulcers and atopic dermatitis. As the field continues to expand its understanding of the mechanisms by which this pathogen rapidly develops resistance to new antibiotics, the underlying mechanisms that facilitates niche adaptation and host colonization among healthy individuals remain elusive.

Bacterial and host lipid metabolism presents and area of renewed interest in understanding the pathogenesis of S. aureus. Furthered by discoveries of fatty acid piracy, strain-to-strain variability and the availability of better tools to assay and quantify lipid compositions, research on S. aureus lipid metabolism and its effectors presents the potential of identifying key mechanisms utilized by this pathogen to enable niche adaptation prior to an infection. There were two main aims to this work, first to adapt and apply emerging methods in mass spectrometry-based lipid analysis to quantify and characterize the interactions of S. aureus with the host lipidome. Results from this demonstrate the presence of strain to strain heterogeneity based on lipid metabolism and indicate the presence of uncharacterized proteins that mediate lipid modifications. The second aim was to identify and characterize the function of a putative lipase conserved among pathogenic strains of S. aureus and investigate its role in bacterial physiology and pathogenesis. The aims, while distinct, focus on furthering our understanding of the interaction between staphylococcal lipid metabolism and host.

Utilizing type strains to analyze the interaction with a defined lipid formulation by high resolution mass spectrometry, and developing tools to improve and standardize the reporting of lipidomic information, this study demonstrates the variability in lipid metabolism among pathogenic isolates of S. aureus with possible correlations to their sites of isolation. Targeted approaches to characterize the specificity of purified recombinant LipA, resulted in the identification of its specificity for short chain fatty acid esters. LipA was found to be localized to the extracellular face of the bacterial cell envelope and appears to bind specifically to lipids abundant in the bacterial cell membrane. The work presented herein demonstrates that LipA plays a role in resistance to peroxide stress and inhibits keratinocyte migration while having specificity for 1-oleoyl 2-acetyl glycerol (OAG); a potent modulator of mitogen activated protein kinase (MAPKK). This underscores the importance of further characterization of its regulation, mechanism of action and importance to bacterial pathogenesis in in-vivo models of infection.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

1-21-2020

Available for download on Sunday, January 19, 2025

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