Toxic Substance in Culture Filtrate of Vibrio sp. Strain N7802, a Poor Producer of Hemolysin and Protease

Abstract

Culture filtrate of pathogenic Vibrio sp. (strain N7802) was fractionated by DEAE-cellulose ion exchange chromatography. The fraction showing lethal activity in rainbow trout and mice was eluted from the column with linear gradient of NaCl (DII fraction). The first peak (GI fraction) obtained by purification of DII fraction by Sephadex G-200 gel chromatography had lethal toxicity against rainbow trout and mice. Neither protease nor hemolytic activity was observed in the GI fraction. In sodium dodecylsulfate-polyacrylamide disc gel electrophoresis, the GI fraction revealed one protein band with molecular weight of 35 K and one periodic acid-Schiff positive band in the same position as the protein band. These results indicate that Vibrio sp. strain N7802 produced extracellular toxic substance which was distinct from hemolysin or protease and the toxin might play a role in the pathogenesis of vibriosis in rainbow trout.