Properties of proteolytic toxin of Vibrio anguilolarum from diseased flounder |
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| Authors: | Mo Zhao-lan Chen Shi-yong and Zhang Pei-jun |
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| Institution: | (1) Experimental Biology Laboratory, Institute of Oceanology, Chinese Academy of Sciences, 266071 Qingdao, China |
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| Abstract: | Extracellular products (ECP) produced byVibrio anguillarum strain M3 originally isolated from diseased flounder (Paralichthys olivaceus) were prepared. ECP of M3 showed gelatinase, casinase, amylase and haemolytic activity on agarose plates. High protease activity
against azocasin was detected. Bacterium M2 showed highest growth and protease activity at 25°C. The protease present in ECP
showed maximal activity at pH 8 and 55°C; was completely inactivated by application of 80°C heat for 30 min; was completely
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 protein/g body weight. The addition of HgCl2 and application of heat at 50°C decreased the lethal toxicity of ECP. When heated at 100°C, ECP lethality to flounder was
completely inhibited. After intramuscular injection of ECP into flounder, it showed evident histopathological changes including
necrosis of muscle, extensive deposition of haemosiderin in the spleen, dilated blood vessels congested with numerious lymphocytes
in the liver. These results showed that ECP protease was a lethal factor produced by the bacteriumV. anguillarum M3.
Contribution No. 4213 from the Institute of Oceanology, Chinese Academy of Sciences.
Funded by projects under the Major State Basic Research Development Program, Grant G1999012003. |
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| Keywords: | Vibrio anguillarum extracellular products protease toxicity |
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