Hemolysin from Edwardsiella tarda strain ET16 isolated from eel Anguilla japonica identified as a hole-forming toxin

Edwardsiella tarda strain ET16 isolated from the liver of diseased eel Anguilla japonica could secret a hemolysin across cell membrane rather than cell-associated hemolysins that are reported by most known E. tarda strains. Hemolysin exported to the culture medium was partially purified by the application of Sephacryl S-100 HR and DEAE-Sephacel. The molecular weight of the functional hemolysin protein was estimated to be approximately 34 kDa by the recovery of hemolytic activity in situ after SDS-PAGE. The action of the hemolysin on tilapia erythrocytes was scrutinized under SEM. E. tarda hemolysin caused holes between 0.5-2.5 mu m in diameter to be formed on the membrane of the tilapia erythrocytes.