Characterization of extracellular products from an isolate of Vibrio harveyi recovered from diseased post-larval Penaeus vannamei (Bonne)

摘要

V. harveyi recovered from diseased post-larval Penaeus vannamei produced a thermostable exotoxin, which was lethal to Dublin Bay prawns, Nephrops norvegicus L., when injected intramuscularly. The extracellular products (ECPs) concentrated from tryptone soya broth supplemented with 1% (w/v) sodium chloride or from cellophane overlays on marine 2216E agar with incubation at 15, 22 and 27deg C were toxic, with the lethal dose 50% of the crude ECPs estimated to be 4.4μg protein per prawn. Proteolytic, haemolytic and cytotoxic activities were detected, although the occurrence and quantity of these activities were influenced by cultural conditions. The ECPs which had been heated (100deg C for 10 min) or digested with protease K produced the same pathology ascrude, untreated ECPs. Western blotting demonstrated that all the ECP preparations contained low molecular weight lipopolysaccharides, which may constitute the lethal toxin of V. harveyi.