Comparison of Gliding Bacteria Isolated from Fish in North America and Other Areas of the Pacific Rim

Twenty-six isolates of gliding bacteria associated with columnaris disease were collected from different species of fish from a wide geographic range. Although there were three phenotypic variations in colony morphology among the strains observed, the growth and biochemical characteristics, as well as, GC content revealed no differences among these isolates. However, when compared by DNA hybridization, there appeared to be three distinct groups based on the DNA homology. Eighteen of the twenty rhizoid strains represented the first group. They were 81-98% homologous with Pacific Northwest strain DD3 of Flexibacter columnaris and included isolates from Canada, Chile, Japan, Korea, ROC and the USA (Atlantic and Pacific Coasts). The mucoid strain K4m was 95% homologous with strain DD3. Taiwanese strains 4G and 5F belonged to the second group and could be classified into new species of gliding bacteria as a result of low DNA homology (<29%) to the Pacific Northwest strain of F. columnaris. A strain with a honeycomb-like colony morphology which came from the southern portion of the USA represented a third group, was less homologous (73%) with strain DD3 of F. columnaris.