Date of Award

Summer 8-2022

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Rebecca Giorno-McConnell

Abstract

A significant impending threat to the public health system is the rise of multidrug resistant bacteria. An attractive potential option to combat this is antimicrobial peptides (AMPs). AMPs are peptide chains with lengths that range from 10 to 70 amino acid residues that show antimicrobial activity. AMPs tend to have less toxicity than other antibiotic therapies, have a broader range of activity, and have a decreased resistance development by the target cells. Short AMPs are especially attractive due to their stability as well as their ability to penetrate cell membranes. With a wide range of possible AMPs available, further characterization of these molecules is needed before using AMPs in a clinical setting. For this study, 4 previously identified AMPs (WLRRIKAWLRR [RR], WLRRIKAWLRRIKA [RIKA], IIGGR [IGR], and HPQYNQR [HQ]) were synthesized using solid phase peptide synthesis and evaluated for antimicrobial activity. Previous studies regarding MIC assay methods indicate that special considerations, such as test vessel material and growth media, are required for AMPs to obtain accurate MIC data. Therefore, a resazurin colorimetric assay was conducted in a 96-well polypropylene microtiter plate with iso-sensitest broth. Eight species were challenged with these 4 peptides, many for the first time. Peptides RR and RIKA demonstrated antimicrobial activity in 6 and 7 species, respectively. RIKA consistently demonstrated more antimicrobial activity than RR. IGR and HQ showed no antibiotic activity in this study.

This novel study involved synthesizing four AMPs, designing a novel experimental method for antibiotic activity of AMPs, and expanding antimicrobial activity testing to eight bacterial species to allow for a comprehensive comparison of these potential novel antibiotic therapies. This comparison could renew interest in these AMPs and possible combination therapies.

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