Five strains (9L, 642A, 714, 5688T and 3384Y) of Histophilus ovis were investigated with respect to iron acquisition. All strains used ovine, bovine and goat, but not porcine or human, transferrins (Tfs) as iron sources for growth. In solid phase binding assays, total membranes from only two (9L and 642A) of the five strains, grown under iron-restricted conditions, were able to bind Tfs (ovine, bovine and goat, but not porcine or human). However, when the organisms were grown under iron-restricted conditions in the presence of bovine Tf, total membranes from all strains exhibited Tf binding (as above); competition experiments demonstrated that all three Tfs (ovine, bovine and goat) were bound by the same receptor(s). An affinity isolation procedure allowed the isolation of two putative Tf-binding polypeptides (78 and 66 kDa) from total membranes of strains 9L and 642A grown under iron-restricted conditions, and from membranes of all strains if the growth medium also contained Tf. A gene encoding a Pasteurella multocida TbpA homologue was shown to be present in each of two representative strains (9L and 3384Y); these genes were sequenced and determined to be the structural genes encoding the 78-kDa Tf-binding polypeptides. The identification of a fur homologue and a Fur box within the promoter region of tbpA in both strains indicated that Fur (and iron) is responsible for the iron-repressible nature of Tf-binding activity. Although tbpA transcripts were detected by reverse transcription (RT)-PCR with RNA isolated from strains 9L and 3384Y grown under iron-restricted conditions, with strain 3384Y, and depending on the primer pair, tbpA transcripts were detected by RT-PCR predominantly when the RNA was isolated from cells grown under conditions of iron-restriction in the presence of Tf. The presence of an additional G in the tbpA gene of strain 3384Y grown under iron-replete conditions, compared to organisms grown under iron-restricted conditions plus bovine Tf, is
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.38481 |
| Date | January 2002 |
| Creators | Ekins, Andrew John |
| Contributors | Niven, D. F. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Natural Resource Sciences.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001956434, proquestno: NQ85703, Theses scanned by UMI/ProQuest. |
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