The present study investigated antibacterial peptides in rainbow trout. Oncorhynchus mykiss. The growth inhibition zone assay was optimised for use with fish bacterial pathogens. Magainin 1 was inactive against all bacteria tested while cecropins P1 and B were very efficient against all Gram negative fish pathogens. The A-layer of Aeromonas salmonicida had a protective effect against cecropins. Cecropin B was more potent and had a wider spectrum of activity than cecropin P1. Defensin HNP-2 was active against three Gram positive bacteria and one Gram negative bacterium. The most sensitive strain to cecropins, A. salmonicida MT004, was chosen as the test microorganism. Purification of antibacterial compounds from rainbow trout was optimised using solid-phase extraction followed by reverse-phase C8 HPLC. Five HPLC peaks purified from gut leucocyte culture supernatants contained inducible antibacterial molecules including a 2131Da-peptide. Five antibacterial HPLC peaks obtained from blood leucocyte culture supernatants contained inducible antibacterial compounds. The most potent weighed 2149g/mol. Its small size, high potency and rapid induction post-challenge would potentate its development as a therapeutic agent. Eight very potent antibacterial peptides weighing between 2500 and 8800g/mol were isolated from serum. The N-terminal sequences of three of them, weighing 2595, 7942 and 7931Da respectively were determined and they were named salmocidins 1, 2 and 3 respectively. The effect of different stimuli on their production was assessed by HPLC and indirect ELISA using a specific polyclonal antibody raised against salmocidin 1. Salmocidin 1 was particularly interesting (large peak on reverse-phase HPLC facilitates its isolation; potency against the test microorganism, small size therefore potentially cheap to synthesise chemically). Salmocidin 1 is a very interesting, novel antibacterial peptide that may provide a satisfactory alternative to antibiotics in fish farming and may find clinical.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:592564 |
| Date | January 1999 |
| Creators | Henry, Morgane Annie |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU123741 |
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