| Summary: | 碩士 === 國立海洋大學 === 水產養殖學系 === 87 === Aeromonas hydrophila strain AH20 was isolated from Corydoras aeneus which shown the symptom of hemorrhage. A plasmid, pPH4, which carry a unique aerolysin sequence was labeled by DIG and used as a probe to hybridize strain AH20 chromosomal DNA. Homologous DNA residing in the AH20 genome could not be detected. Enzymatic activity of either protease or phospholipase C, both are postulated to be virulent factors to destroy red blood cell (RBC) membrane and consequently resulting in hemolysis. An interesting characteristic of this strain AH20 is observed as that the secretion of hemolysin is growth-phase dependent. The highest hemolytic unit was monitored in the late log-growth phase, then decline soon. On the other hand, while entering into the stage of stationary-phase, AH20 began to export phospholipase C only in the stationary phase and sustain 30-40 hours. Yields of concentrated extracellular products (ECP) from the culture in the state of late log phase were resolved by Sephacryal S-100 HR chromatography. The partial purified ECP from the collected eluents were mixed with tilapias'' erythocyte''s membrane for enzymatic digestion. Function of degrading RBC membrane proteins which determined by SDS-PAGE resulted in the conclusion of that the hemolysin exporting by strain AH20 is due to the activity of protease not phospholipase C.
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