Project Director

Giles, David K.

Department Examiner

Chapman, Elise; Spratt, Henry G.


Dept. of Biological and Environmental Sciences


University of Tennessee at Chattanooga

Place of Publication

Chattanooga (Tenn.)


As antibiotic resistance becomes a major challenge for public health professionals, our research objectives aimed to investigate the potential for polyunsaturated fatty acids (PUFAs) to create membrane vulnerability in the gram-negative pathogen Vibrio cholerae to help improve the efficacy of several antibiotics. V. cholerae, normally residing in aquatic environments, is capable of altering its phospholipid composition through the uptake and assimilation of exogenous polyunsaturated fatty acids. The purpose of this study was to measure PUFA-mediated changes in the membrane permeability and antibiotic resistance of Vibrio cholerae. The three physiologically relevant PUFAs used were linoleic acid [18:2], arachidonic acid [20:4], and docosahexaenoic acid [22:6]). Bacterial membrane permeability was measured using a crystal violet assay with each PUFA resulting in at least a 10% change in uptake of the dye. When the cyclic peptides polymyxin B (PMB) and colistin were administered at subinhibitory concentrations, PUFA-specific permeability trends were observed. The availability of PUFAs caused significant changes to the minimum inhibitory concentrations (MICs) of PMB, colistin, LL-37, and Cecropin A. Strikingly, PMB and colistin were found to decrease the MIC by at least 4-fold. Not only did 18:2, 20:4, and 22:6 alter bacterial permeability, but they also induced vulnerability to PMB and colistin in V. cholerae, perhaps suggesting synergistic potential in the control and prevention of pathogens. 18:2 did not affect MICs of LL-37 and Cecropin A whereas, the addition of 20:4 and 22:6 increased the MICs by at least 2-fold.


I would like to thank Dr. Giles for being my thesis director and allowing me to work on this research project during the Covid-19 pandemic. He has been an excellent mentor and has taught me many concepts about microbiology and how to do research in the past year and half. I know these skills will help me as I enter the medical field, and I appreciate his efforts to push me to be the best student that I can be. I would also like to thank both Dr. Chapman and Dr. Spratt for taking the time to serve on my committee. Their feedback has been valuable, and I appreciate all their guidance and willingness to mentor students such as myself. This work was supported by the Center of Excellence in Applied Computational Science and Engineering (CEACSE) grant from the University of Tennessee at Chattanooga awarded to Dr. David Giles.


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.




Vibrio cholerae; Unsaturated fatty acids; Peptide antibiotics


Antimicrobial Peptides; Vibrio cholerae; PUFAs



Document Type



44 leaves.







Date Available


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Bacteria Commons