碩士 / 國立海洋大學 / 水產養殖學系 / 90 / This study investigated the pathogenesis of Photobacterium damsela subsp. piscicida (strain C.P.), isolated from swollen kidney of diseased cobia (Rachycentron canadum) in the fish. Virulence of the bacterial cells was compared to that of Vibrio alginolyticus (strain C3c) and V. carchariae (strain C3d) isolated from kidney of diseased cobia as well.
The virulence tests were conducted in cobia (10g) and the LD50 values of Ph. damsela subsp. piscicida (strain C.P.), V. alginolyticus (strain C3c) and V. carchariae were 1.03 × 104, 3.28 × 104 and 7.48 × 104 CFU / g fish body weight, respectively, Ph. damsela subsp. piscicida (strain C.P.) was more virulent than the other two vibrio species. The LD50 value of extracellular products (ECP) from strain C.P. in cobia (10g) was 1.26 *g protein / g fish body weight.
Protease was partially purified from ECP of Ph. damsela subsp. piscicida (strain C.P.) by using anion exchange columns (Q Sepharose High Performance, RESOURCE Q and Mono Q) on Fast Protein Liquid Chromatography (FPLC). Partially purified protease fraction contained 7.2 KDa and 34.3 KDa protein band on SDS — PAGE with the latter band band exhibiting protease activity. The fraction was lethial to cobia, haemolytic (210 haemolytic units / mg protein) against erythrocytes of cobia, caseinolytic and heat-labile with optimal pH values between 6 and 8. As protease activity in the fraction was completely inhibited by the presence of L-cysteine, EDTA, EGTA, 1-10 phenanthroline, TPCK and TLCK, it was suggested to be a metallo-protease. However, about 70% of protease activity in the fraction was also inhibited by SDS. This metallo-protease may play an important role in the pathogenesis of Ph. damsela subsp. piscicida infection in the cobia.
| Identifer | oai:union.ndltd.org:TW/090NTOU0086024 |
| Date | January 2002 |
| Creators | 林積陽 |
| Contributors | 劉秉忠 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 0 |
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