CAJ | 학술논문

Extracellular products (ECP) produced by Vibrio anguillarum strain M3 originally isolated from diseased flounder (Paralichthys olivaceus) were prepared. ECP of M3 showed g elatinase, casinase, amylase and haemolytic activity on agarose plates. High protease activity against azocasin w as detected. Bacterium M3 showed highest growth and protease activity at 25℃. The protease present in ECP showed maximal activity at pH 8 and 55℃; was completely inactivated by application of 80℃ heat for 30 min; was com pletely inhibited by EDTA and HgCl2, and was partially inhibited by PMSF, SDS, MnCl2 and iodoacetic acid; but not inhibited by CaCl2 and MgCl2. The ECP was toxic to flounder fish at LD50 values of 3.1 μg prot ein /g body weight. The addition of HgCl2 and application of heat at 50℃ decreased the lethal toxicity of ECP. When heate d at 100℃, ECP lethality to flounder was completely inhibited. After intramuscular injection of ECP into flo under, it showed evident histopathological changes including necrosis of muscle, extensive deposition of haemosiderin in the spleen, dilated blood vessels congested with numerous lymphocytes in the liver. These re sults showed that ECP protease was a lethal factor produced by the bacterium V. anguillarum M3.