Extracellular Proteases from Aeromonas hydrophila: Partial Purification and Effects on Age-0 Channel Catfish

Abstract

Extracellular products from Aeromonas hydrophila strain 22 grown in a defined medium were lethal to young-of-the-year channel catfish Ictalurus punctatus. No detectable hemolysin was produced, but partial purification and characterization of the extracellular products suggested that the lethal factors were proteases. The median lethal dose (LD50) of a heat-labile protease fraction was 18.0 μg protein per gram of fish. A heat-stable protease fraction gave an LD50 of 3.0 μg protein per gram of fish.