Deoxyribonucleic acid relationships among marine vibrios pathogenic to fish

Polynucleotide sequence relationships among 19 strains of marine vibrios, 15 of which were pathogenic to fish, were assessed by analysis of DNA-DNA homo-and hetero-duplexes with the endonuclease S1. DNA base compositions (mole% guanine-cytosine (GC) of selected vibro strains were determined by thermal denaturation. Pathogenic strains from the Pacific Northwest had identical mole% GC but could be divided into two discrete, yet related, DNA-homology groups. One highly related group was typical of Vibro anguillarium and showed greater than 70% within-group polynucleotide sequence homology. Second group (designated V1669) showed greater than 83% within-group homology but only about 60% relatedness to V. anguillarum. Neither group showed a significant degree of relatedness to V. parahaemolyticus (biotypes parahaemolyticus or alginolyticus) or to representative strains of any of the other previously described homology groups which we tested.