碩士 / 國立臺灣大學 / 動物學研究研究所 / 93 / Nervous necrosis virus （NNV） is a critically important pathogen for reared marine fish, and has caused mass mortality in more than 30 fish species in recent 10 years. In this study, we cloned anti-NNV bacteria from the intestinal microflora of grouper, and investigated the possibility of using intestinal bacteria as a biological control for viral nervous necrosis（VNN） disease. The normal flora from grouper intestine was first isolated and preliminary identified by GFB-14E system. The bacteria secreting substance against grouper NNV（GNNV） were selected according to the result of neutralization test. Three bacterial strains with high neutralization titers（Log NI >5） against GNNV were selected for further characterization. It was found that the anti-GNNV substances in the culture supernatants of these selected clones were stable after 100 °C for 10 minutes treatment. The size range of anti-GNNV substances was estimanated by microfilter with different pore sizes. The size of anti-GNNV substance of one bacteria strain is between 3-5 kDa, and of another two strains is smaller than 3 kDa. After 100 °C 10 min and microfilter treatment, the protein concentration of bacterial supernatant declined to zero, but their anti-NNV activities were still high. Therefore, it is revealed that the anti-GNNV substances are small molecule and heat-resistant. In the feeding test, the cultured-bacteria were mixed with commercial food and fed grouper larvae for 4 weeks and then challenged with GNNV by intra-peritoneal injection. The accumulated mortality of negative control fish was 24%, and over 50% of fishes showed clinical symptom of VNN. However, the accumulative mortality of the fed groups was zero, and the fishes were very healthy. The intestinal flora of groupers was examined, and the compositions of intestinal flora of the fed groupers were different from that of the negative control fish.
| Identifer | oai:union.ndltd.org:TW/093NTU05312030 |
| Date | January 2005 |
| Creators | Li Chang, 張莉 |
| Contributors | 齊肖琪 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 67 |
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