Symes, Steven J.
Giles, David K.; Knight, Kyle S.
University of Tennessee at Chattanooga
Place of Publication
Multi-drug resistant bacteria have become problematic in healthcare settings. Recent studies have documented the ability of some bacteria, such as Vibrio species, to assimilate exogenous fatty acids into their membrane phospholipids. Therefore, the current research was performed to determine whether the three virulent, multi-drug resistant bacteria Acinetobacter baumannii, Klebsiella pneumoniae, and Escherichia coli can remodel their cell membranes following exposure to a range of exogenous polyunsaturated fatty acids (PUFAs). Furthermore, we hypothesized that PUFAs would influence phenotypes associated with growth and virulence. Extracted phospholipids were examined by UPLC/MS analysis to confirm assimilation of exogenous PUFAs into the bacterial phospholipids. A. baumanii, K. pneumoniae, and E. coli were found to incorporate all exogenous PUFAs into their cell membranes, with the exception of docosahexaenoic acid (22:6) for E. coli. Membrane permeability assays were performed using Crystal violet (CV) and ethidium bromide (EtBr). Notably, E. coli samples exposed to 22:6 or arachidonic acid (20:4) took up approximately 35% or 60% more CV than the control sample, respectively. All PUFA-exposed E. coli samples demonstrated higher uptake of EtBr than the control sample, suggesting that every fatty acid tested increased membrane permeability. An assay for biofilm formation revealed that α-linolenic acid (18:3α), γ-linolenic acid (18:3γ), 20:4, and 22:6 significantly (p < 0.002) increased biofilm production in E. coli. Strikingly, 18:3 γ and 20:4 tripled biofilm formation when compared to the control sample. Similar phenotypic shifts were observed in A. baumannii and K. pneumoniae. Motility assays and minimum inhibitory concentration (MIC) assays using membrane-active cyclic peptide antibiotics were also performed. Taken together, the results of the experiments presented in this thesis suggest that exogenous PUFAs may be utilized in the future as combatants of multi-drug resistant bacteria in conjunction with antibiotics.
I want to thank Dr. Steve Symes for giving me the opportunity to participate in this research and for his outstanding performance as my thesis director and mentor over the course of the project. Dr. Symes was always thorough in his explanations, patient and helpful as I learned new things, willing to learn new things himself, and supportive of my academic growth through each step of the way. I also want to thank Dr. David Giles. Dr. Giles was a mentor to me over the course of this project as well and was instrumental in helping me understand the biological aspect of the research. Dr. Giles was also kind, patient, supportive, and trusting of me, and always answered my questions to the best of his ability with enthusiasm. Thank you, Dr. Symes and Dr. Giles! I feel truly fortunate to have had both of you as my mentors during this project. I would also like to thank the previous students that have participated in this research, notably Derek Anderson, for helping to lay the foundation that the research in this thesis was built upon. I want to thank the Grote Chemistry fund, the Westbrook Research Scholarship, and the National Science Foundation for the funding that made this research possible.
B. S.; An honors thesis submitted to the faculty of the University of Tennessee at Chattanooga in partial fulfillment of the requirements of the degree of Bachelor of Science.
Anti-infective agents; Drug resistance in microorganisms
Herndon, Josh, "Phospholipid membrane remodeling through exogenous fatty acid incorporation in certain bacterial species" (2018). Honors Theses.
Available for download on Wednesday, May 01, 2019