Vibrio ichthyoenteri sp. nov., a Pathogen of Japanese Flounder (Paralichthys olivaceus) Larvae

Abstract

Seven similar strains which were pathogens of Japanese flounder (Paralichthys olivaceus) larvae with opaque intestines had characteristics of the genus Vibrio. These strains were divided into two genomic species (species 1 containing six strains, and species 2 containing one strain) on the basis of the results of DNA-DNA hybridization experiments in which the membrane filter method was used, and these two species could be differentiated from each other by the following characteristics: acid production from d-galactose and utilization of d-glucuronate and β-hydroxybutyrate. Strain F-2, the type strain of species 1, exhibited levels of DNA relatedness with 29 previously described Vibrio species of 5 to 18%. The flounder isolates belonging to species 1 were also differentiated from the previously described Vibrio species phenotypically by the following characteristics: they were nitrate reduction positive; each cell had a single polar flagellum; they did not produce arginine dihydrolase, chitinase, gelatinase, and lipase; they did not utilize d-cellobiose and citrate; and they did not grow at 35°C. The G+C contents of the DNAs of four species 1 strains were 43 to 44 mol%. The name Vibrio ichthyoenteri sp. nov. is proposed for genomic species 1. The type strain of V. ichthyoenteri is strain F-2 (= IFO 15847). Species 2 was also considered a new genomic species, but a species name is not proposed in this paper because only one strain is available and the phenotypic variability of the species is not known.