PURIFICATION OF A LETHAL TOXIN OF EDWARDSIELLA-TARDA

PL toxin lethal to fish was purified from extracellular products (ECP) of Edwardsiella tarda by ion exchange chromatography and gel filtrati on. The purified toxin is a protein having proteolytic activities and lethal toxicity to Japanese eel Anguilla japonica with the LD(50) of 1 .6 mu g per g of fish body weight. Molecular weight of the protein was estimated to be 37 kDa by SDS-PAGE. SDS-PAGE, Western blot and immuno diffusion analyses revealed that the 37 kDa protein was present in the ECP and TCC (intracellular components) of virulent strains of E. tard a but not in those of avirulent strains, indicating that this toxin pl ays an important role in the pathogenicity of E. tarda.