EFFECT OF SODIUM CHLORIDE ON PRODUCTION AND TOXICITY OF EXTRACELLULAR PRODUCTS OF EDWARDSIELLA TARDA

摘要

The effect of NaCl concentration in the culture medium on the production and toxicity of Edwardsiella tarda extracellular products (ECP) was studied. Edwardsiella tarda (FK1051) was cultured in a peptone-yeast extract broth supplemented with 3% NaCl (3%-NaCl culture) and without NaCl (0%-NaCl culture). The ECP of both cultures were prepared by the cellophane plate method. The wet bacterial weights and the protein concentrations were detected at different time intervals. The bacterial weights decreased after 2-3 days incubation and thereafter the ECP protein levels increased. The protein concentration in ECP of 3%-NaCl culture was higher than that of 0%-NaCl culture. SDS-PAGE revealed the appearance of new bands (35 and 70 kDa) and intensification ofother bands in the ECP of 3%-NaCl culture. The intramuscular injection of ECP in goldfish revealed higher toxicity in the 3%-NaCl culture. These results suggest that the NaCl-induced ECP toxicity of E. tarda may play a vital role in its virulence.