When
Presenter:
Dr. Kelly Hines
Assistant Professor, Department of Chemistry, University of Georgia
Abstract:
Staphylococcus aureus varies its membrane fluidity in response to environmental stresses by changing the ratio of branched-chain fatty acids (BCFAs) to straight-chain fatty acids (SCFAs) in its membrane lipids. Altered membrane fluidity has been associated with an increased tolerance of membrane-targeting antibiotics, including daptomycin. The routine assessment of microbial membrane fluidity relies on the measurement of total BCFA-versus-SCFA determination by GC-MS. Although GC-MS is capable of resolving BCFA and SCFA isomers, the requirement of free fatty acids eliminates the possibility to evaluate the preferences of lipid subclasses for BCFAs vs. SCFAs. We recently demonstrated a RPLC method that can separate lipid isomers having branched-branched, branched-straight, or straight-straight fatty acyl tail combinations. Using this approach and stable isotope labeling, we examined the distribution of FA isomers in the lipids of a S. aureus strain with daptomycin resistance. A strain of S. aureus N315 with high-level daptomycin resistance was found to have substantially more BCFAs in its membrane lipids compared to the isogenic parent N315, which correlated with increased membrane fluidity. Despite the preference for BCFAs is the resistant strain, we found that both organisms could utilize SCFAs when provided in the culture broths. This supplementation reversed the resistant strain’s membrane fluidity towards that of the parent strain. These results indicate that daptomycin resistance can be facilitated in-part by increased membrane fluidity, and support the concept of targeted remodeling of the S. aureus membrane to mediate antibiotic resistance.
Biosketch:
Kelly Hines is an Assistant Professor in the Department of Chemistry at the University of Georgia. Kelly graduated from the University of Florida in 2009 with a B.S. in Chemistry. She completed her Ph.D. in Chemistry at Vanderbilt University with John A. McLean, where she used ion mobility-mass spectrometry (IM-MS) to identify of metabolite, lipid, and peptide signatures of disease from complex biological samples. After receiving her Ph.D. in 2014, Kelly completed a one-year postdoctoral fellowship in the Mayo Clinic Regional Metabolomics Core where she established quantitative MS methods for lipidomics and protein metabolism. In 2015, Kelly joined the lab of Libin Xu at the University of Washington School of Pharmacy. Her work in the Xu Lab, supported in part by a U.S. Pharmacopeial Convention (USP) Global Fellowship, focused on high-throughput IM-MS measurements of drugs and small molecules, and LC-IM-MS methods for lipidomics. She joined the faculty at UGA in 2019, where her lab is using lipidomics to study the role of lipids in host-pathogen interactions and antibiotic resistance. Kelly has been recognized as a Female Role Model in Analytical Chemistry by Analytical and Bioanalytical Chemistry, an Outstanding Emerging Investigator by the Journal of the American Society for Mass Spectrometry, and is the recipient of an ASMS Research Award.