Polyphasic Taxonomy of the GenusVibrio:Numerical Taxonomy ofVibrio cholerae, Vibrio parahaemolyticus, and RelatedVibrioSpecies

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Abstract
A set of 86 bacterial cultures, including 30 strains ofVibrio cholerae, 35 strains ofV. parahaemolyticus, and 21 representative strains ofPseudomonas, Spirillum, Achromobacter, Arthrobacter, and marineVibriospecies were tested for a total of 200 characteristics. Morphological, physiological, and biochemical characteristics were included in the analysis. Overall deoxyribonucleic acid (DNA) base compositions and ultrastructure, under the electron microscope, were also examined. The taxonomic data were analyzed by computer by using numerical taxonomy programs designed to sort and cluster strains related phenetically. TheV. choleraestrains formed an homogeneous cluster, sharing overall S values of ≥75%. Two strains,V. choleraeNCTC 30 and NCTC 8042, did not fall into theV. choleraespecies group when tested by the hypothetical median organism calculation. No separation of “classic”V. cholerae, El Tor vibrios, and nonagglutinable vibrios was observed. These all fell into a single, relatively homogeneous,V. choleraespecies cluster.V. parahaemolyticusstrains, excepting 5144, 5146, and 5162, designated members of the speciesV. alginolyticus, clustered at S ≥80%. Characteristics uniformly present in all theVibriospecies examined are given, as are also characteristics and frequency of occurrence forV. choleraeandV. parahaemolyticus. The clusters formed in the numerical taxonomy analyses revealed similar overall DNA base compositions, with the range for theVibriospecies of 40 to 48% guanine plus cytosine. Generic level of relationship ofV. choleraeandV. parahaemolyticusis considered dubious. Intra- and intergroup relationships obtained from the numerical taxonomy studies showed highly significant correlation with DNA/DNA reassociation data.