Pathogenic Vibrio isolated from cultured eels. IV. Deoxyribonucleic acid studies.

Abstract

The molecular taxonomic position of a new pathogenic vibrio isolated from cultured eels has been studied. The bacterium had been classified as V. anguillarum Type B, V. anguillarum f. anguillicida, on the basis of phenotypic properties. The percent guanine plus cytosine content of deoxyribonucleic acid (DNA) was 46.3%, which is within or appreciably close to the DNA base composition ranges of the existing Vibrio species. Polynucleotide sequence analysis by means of optical measurement of renatured DNA, however, provided proof that the present vibrio was distinct from the existing species of the genus Vibrio. The isolates from diseased eels represented a homologous group (96-97% homology for reference ET-7617 strain DNA) with the genome size of 2, 000 to 2, 500×106 daltons. On the other hand the reference strain was very distantly related to other Vibrio species: 12-23% related to V. anguillarum; 2-17% to V. fischeri; 14% to V. parahaemolyticus; 12% to V. alginolyticus; 9% to V. cholerae. Therefore the present organism was considered as a new member of the genus Vibrio.