DOI
https://doi.org/10.25772/G1T3-KB13
Author ORCID Identifier
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
Included in
Biochemistry Commons, Bioinformatics Commons, Investigative Techniques Commons, Microbial Physiology Commons, Pathogenic Microbiology Commons