Bacteria have strain-dependent host attachment mechanisms. Bacteria with pili, also called fimbriae, attach to the host epithelial cells allowing the bacterium time to adhere, form biofilms, and infect the body without being flushed out by the host’s cleansing mechanisms. Haemophilus influenzae type B (Hib) are bacteria that colonize the human nasopharynx by attaching via adhesion pili to the microvilli found in the respiratory tract. To gain insight into the attachment mechanism of Hib bacteria, pilus expression and purification were optimized.
To determine the structure of Hib pili, cryogenic electron microscopy (cryo-EM) images were collected of the isolated and purified filaments. Reconstructions were computed and the secondary structure of the Hib subunit (HifA) was predicted and fitted into the reconstruction. The structure of the Hib filament showed the pili to have one-start helical symmetry, with a zigzag shape. The predicted structure of HifA had two regions of interaction with the adjacent subunit, including an N-terminal extension (NTE) and a loop, both extending from the immunoglobulin (Ig)-like domain. These extensive contacts resulted in a stronger interaction between the subunits compared to other types of adhesion pili.
Toward the goal of inhibiting pili adherence to the host cells, the effects of salivary peptides were tested. Peptide binding assays were performed and analyzed to determine changes in structure or macromolecular assembly of Hib pili. Our discovery of the presence and absence of pilus three-dimensional bundling and two-dimensional networks can aid in the future prevention of bacterial colonization and infection within the human body thereby preventing Hib related diseases.
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/48087 |
| Date | 13 February 2024 |
| Creators | Thairatana, Siriratt |
| Contributors | Bullitt, Esther, Atkinson, David |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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