Giles, David K.
Chapman, Elise; Alda, Fernando
University of Tennessee at Chattanooga
Place of Publication
Antimicrobial peptides are found in all organisms and have gained notoriety in recent years for their effectiveness against a variety of pathogens. Piscidins, first isolated from the mast cells of vertebrates, comprise a family of these host defense peptides. Piscidins 1 (P1) and 3 (P3), found in sea bass and other fishes, are isoforms with different modes of action. P1 induces membrane perturbation, while P3 binds DNA to exert antibacterial activity. Each has the ability to bind Cu2+ (P1Cu and P3Cu) which dramatically impacts their antimicrobial characteristics. The purpose of this study was to investigate the activity of metallated and nonmetallated P1 and P3 on Vibrio cholerae, a Gram-negative bacterium of medical importance that normally inhabits an aquatic environment, often associating with fish and other marine life. Known to assimilate exogenous fatty acids into membrane phospholipids, V. cholerae possesses the ability to modify membrane permeability depending upon environmental fatty acid availability. Herein we investigated both permeability and antimicrobial effects of P1, P1Cu, P3, and P3Cu on V. cholerae grown in the presence and absence of linoleic acid (18:2), arachidonic acid (20:4), and docosahexaenoic acid (22:6). Membrane permeability was assessed using a crystal violet assay. These experiments observed a marked decrease (~15%) in permeability when the bacteria is provided each of the fatty acids. All piscidins elicited heightened permeability, with 18:2 decreasing the effect for nonmetallated forms of the peptide. Furthermore, some piscidins displayed concentration dependence with regard to permeability effects. The minimum inhibitory concentrations (MICs) for P1 were increased 2-fold when any of the fatty acids were available. The MIC of P1Cu increased 2-fold with 20:4 and 4-fold with 22:6. The MIC of P3 decreased 2-fold with 20:4 and 4-fold with 18:2. The MIC of P3Cu increased 2-fold with 20:4. Not only do piscidins alter bacterial membrane permeability and display promising antimicrobial capabilities, but the observed effects of exogenous fatty acid supplementation could also hold potential for targeted treatment of infectious disease.
Dr. David Giles, Research Director; Dr. Myriam Cotten, Collaborator
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.
Peptide antibiotics; Unsaturated fatty acids
[iii], 39 leaves
Allen, Elizabeth, "Examining the effects of exogenous polyunsaturated fatty acids on the antimicrobial activity of piscidins in Vibrio cholerae" (2021). Honors Theses.