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In recent years, the skin and muscle hemorrhagic ulcer occurred in grouper hatchery, suggesting that the bacteria extracellular protease was involved. In this study I surveyed the extracellular protease activity of marine bacteria and investigated the characteristics of the pathogen isolated from diseased grouper. The sampling sites of background survey were located along the coast of Taitung. The cultured media were MB2216 and PPESII. The extracellular protease activity was measured using milk seawater medium (MS) and dye-modified proteins of azocasein and azoalbumin. The extracellular protease activities of the marine bacteria were 1~5 U/mg. The average protease activities of the bacteria from MB2216 media were higher than those from PPESII media. The extracellular protease activity assay using azocasein and azoalbumin had similar tendency but the result by the clear zone measurement on the MS medium was of high variations. The FI-02 isolated from the diseased grouper skin was identified as Aeromonas hydrophila by the biochemicial characteristics and 16S rDNA sequence analysis. FI-02 was able to grow on the LB broth with 0~4% NaCl. The FI-02 was resistant to ampillicin, cefazolin, erythomycin, sulfisoxazole, whereas it was sensitive to streptomycin, doxycline, norfloxacin, cefotazime, oxolinic acid, and tetracycline. When FI-02 growing in the four media, the extracellular protease activities were higher than 4 U/mg. The highest protease activity was 6.08 U/mg when the bacteria grew on the LB medium. After heating on 27, 37, 42 and 56¢J for 20 mins, the protease activities remained the same. In the investigation of the fish immunity, owing to the complex compositions of the fish serum, no conclusion can be drawn on the specificity of the antibody against the bacterium.

Thesis (Ph. D.)--Illinois State University, 1984. / Title from title page screen, viewed May 20, 2005. Dissertation Committee: Harry Huizinga (chair), Marcia Miller, Tak Cheung, Mathew Nadakavukaren, Anthony Liberta. Includes bibliographical references (leaves 209-222) and abstract. Also available in print.

Thesis (M. Sc.)--Carleton University, 2001. / Includes bibliographical references (p. 62-71). Also available in electronic format on the Internet.

Wretlind, Heden, and Wadstrom found ammonium sulfate to be inhibitory for the formation of extracellular protease in Aeromonas hydrophila grown in Brain Heart Infusion medium. They demonstrated by manipulating the iron and zinc content within their medium that it is possible to differentially affect the accumulation of hemolysin and protease by A. hydrophila grown in batch culture. Further manipulation of the composition of this medium was done in the present study to determine the effect of other components on the production of protease. The purpose of this study was to determine the factors affecting the level of A. hydrophila protease produced in a chemically defined medium.

This study focused on the enzyme, aspartate transcarbamoylase (ATCase) from A. hydrophila, a Gram-negative bacterium found in fresh water. The molecular mass of the ATCase holoenzyme from A. hydrophila is 310 kDa. The enzyme is likely composed of 6 catalytic polypeptides of 34 kDa each and 6 regulatory polypeptides of 17 kDa each. The velocity-substrate curve for A. hydrophila ATCase is sigmoidal for both aspartate and carbamoylphosphate. The Km for aspartate was the highest to date for an enteric bacterium at 97.18 mM. The Km for carbamoylphosphate was 1.18 mM. When heated to 60 ºC, the specific activity of the enzyme dropped by more than 50 %. When heated to 100 ºC, the enzyme showed no activity. The enzyme's activity was inhibited by ATP, CTP or UTP.

Virulent Aeromonas hydrophila (vAh) is an important emerging bacterial pathogen causing motile Aeromonas septicemia (MAS) in farmed catfish. Understanding the pathogenicity of the disease is essential for the development of preventive measures. In this study, we aimed to develop a bioluminescent virulent A. hydrophila (BvAh) strain to understand the pathogen-host interactions during infection. To achieve this, a new bioluminescence expression plasmid, pAKgfplux3, was constructed and mobilized to vAh. Catfish were challenged with BvAh using immersion, injection, and adipose fin clip procedures, and bioluminescence signal was tracked in live catfish during infection. We developed a novel BvAh strain for the first time, conducted imaging of BvAh in live fish, detected infection routes and attachment sites of the pathogen, and determined target organs, which provided new insights on the pathogenesis of vAh. MAS progressed better in fish when protection of skin was bypassed. Abraded skin seems to provide a potential portal of entry during vAh infection.

Thesis (PhD)--University of South Australia, 1997

Thesis (PhD (Health Science) in Medical Laboratory Science)--University of South Australia, 1995

Thesis (PhD (Health Science) in Medical Laboratory Science)--University of South Australia, 1995