The rapid progression of Klebsiella pneumoniae towards antibiotic resistance is a significant concern, primarily due to its protective extracellular polysaccharide (EPS) capsule that shields the bacteria from host immunity. Our previous research demonstrated that antimicrobial peptides could disrupt the EPS capsule of K. pneumoniae. Further analysis identified Bac7 (1-35), a proline-rich antimicrobial peptide (PrAMP), as having the greatest ability to aggregate with the K. pneumoniae EPS capsule, exhibiting potent antimicrobial activity. However, the relationship between key features facilitating EPS and membrane interactions, as well as antimicrobial efficacy, remains poorly understood. Here, we used natural PrAMPs from diverse organisms to investigate their interactions with the cell envelope of K. pneumoniae. Apidaecin Cd3+, Tur1A, and PR-39 peptides demonstrated activity against all tested strains, with a minimum inhibitory concentration ≤ 1 µg/mL. These peptides shared a proline content exceeding 36% and a charge greater than +5. Active PrAMPs induced membrane depolarization in K. pneumoniae, with the extent of depolarization directly correlating with peptide charge, suggesting membrane depolarization as a potential mechanism for PrAMP entry into the cell. Checkerboard assays of active PrAMPs with PepC, an inactive peptide, suggested the membrane actions of PrAMPs have potential to rescue a therapeutic unable to access the bacterial membrane. Consistent with our findings with bac7(1-35) truncated analogs, both active and inactive PrAMPs aggregated with K. pneumoniae EPS, suggesting that the antimicrobial activities and polysaccharide aggregation potential of this class of peptides can be studied independently.
Furthermore, the treatment of biofilms with active peptides revealed unique structure-based biofilm changes, with Tur1A causing more structural collapse than PR-39. Our findings highlight a potential membrane mediated peptide uptake into the cell which is dependent on the charge of the peptide. Differential biofilm interactions between similar peptides and EPS aggregation of inactive peptides warrant these attributes of PrAMPs to be further studied independently.
| Identifer | oai:union.ndltd.org:ucf.edu/oai:stars.library.ucf.edu:etd2023-1374 |
| Date | 01 January 2024 |
| Creators | Appiah, Ridhwana M |
| Publisher | STARS |
| Source Sets | University of Central Florida |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Graduate Thesis and Dissertation 2023-2024 |
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