The toxR gene of Vibrio anguillarum: Not a virulence regulator but a good tool for diagnosis

Abstract

The toxR gene was cloned from Vibrio anguillarum isolated from diseased Ayu (Plecoglossus altivelis). Analysis of the toxR sequence suggested that the V. anguillarum ToxR is likely to encode the functions shared by ToxRs of vibrios so far reported. There was no significant difference in the ability to produce a protease(s), a hemolysin(s), or in pathogenicity to ayu (intramuscular injection and immersion methods) between PT-24 Δ toxR, an isogenic toxR mutant of PT-24, and PT-24 (an ayu isolate). The expression of two major outer membrane proteins was different between the two strains. The results clearly indicate that ToxR is not involved in regulation of virulence in V. anguillarum and suggest that the ancestral role of ToxR in vibrios is not virulence regulation but regulation of outer membrane expression, in response to environmental change. A DNA probe method and a PCR method targeting the toxR gene were developed for identification of V. anguillarum, and they were shown to be very specific. © 2002, The Japanese Society of Fisheries Science. All rights reserved.