| Summary: | 碩士 === 國立臺灣海洋大學 === 水產養殖學系 === 94 === This study investigated the inhibitory effects, lethal tests in small abalone and the protective effects of bacterial strains possessing alginatase and agarase activities. The probiotic candidates were originally isolated from sea eater raising abalone larvae, substratum of spat settlement and spats.
The probiotic candidates (P1, P2, P3, P4 and P5) were primarily identified by using biochemical tests and molecular sequencing. API 20E, Microgen GN and Biolog GN systems were employed for possible confirmation. The results indicated that strains P1, P3, P4 and P5 belong to Vibrio genus while strain P2 belong to cytophage. All the give strains were sensitive to antibiotics tested except ampicillin(10µg).
All the give strains exhibited no apparent inhibitory effect against pathogenic Vibrio alginolyticus E2-6-2 and V. parahaemolyticus VP2. strains P4 and P5 were lethal to small abalone and could not be used as probiotics.
Strains P1,P2 and P3 were used as probiotic and given to small abalone by injection, feeding or immersion, and then the animals were challenged with V. aliginolyticus or V. parahaemolyticus. The treatment with strain P3 could enhance survival rate of small abalone against Vibrio challenge: for feeding treatment, the increase of survival rates against V. alginolyticus and V. parahaemolyticus were 40 and 27%, respectively; for immersion treatment, the increase of survival rates against the same two Vibrio pathogens were 40 and 53%, respectively.
Strains P3 could survival in the gut of small abalone and its quantity was dose - dependent. It reveals that strain well be a good probiotic candidate against Vibrio infection in small abalone.
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