Modern medicine is challenged continuously by the increasing prevalence of multi-drug resistant bacteria. Therefore, the development of alternatives to traditional antibiotics is an urgent necessity. Cationic antimicrobial peptides (CAMPs) are components of the innate immune defense system. Histones, generally known as proteins that package and regulate the transcription of DNA, share all of the essential antimicrobial traits of CAMPs, and could be promising alternatives to antibiotics. In this study, I investigated the antimicrobial properties of nucleated-erythrocyte-specific linker histone H5 and its derived peptides. Histone H5 was extracted and purified from chicken erythrocytes using an acid extraction followed by ion exchange chromatography using a step salt gradient; the purity (>95%) was verified by densitometry and proteomics analysis. Purified histone H5 demonstrated potent antimicrobial activity against various Gram-positive and Gram-negative planktonic bacteria, including resistant strains such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE), as well as anti-biofilm activity against Listeria monocytogenes and Pseudomonas aeruginosa. Furthermore, scanning electron microscopy (SEM) revealed significant damage to L. monocytogenes and P. aeruginosa bacterial cell surfaces after histone H5 treatment. The potential for histone toxicity towards mammalian cells was investigated with a hemolytic assay which determined that even at the highest concentration tested (1 mg/mL), histone H5 was non-hemolytic. An in silico analysis determined the predicted antimicrobial domain of histone H5 of which six histone H5-derived peptides with potential antimicrobial activity were identified. These six histone H5-derived peptides were synthesized and tested against bacterial pathogens to determine their antimicrobial properties. Although the H5-derived peptides were identified within the predicted antimicrobial domain of histone H5, they did not possess more potent antimicrobial activity than the full length protein. Overall, this study demonstrates that histone H5 and histone H5-derived peptides could be promising candidates in the development of novel anti-infective therapeutics.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/36976 |
| Date | January 2017 |
| Creators | Jodoin, Joelle |
| Contributors | Hincke, Maxwell |
| Publisher | Université d'Ottawa / University of Ottawa |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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