Genotypic heterogeneity of Flavobacterium group IIb and Flavobacterium breve demonstrated by DNA-DNA hybridization.

DNA-DNA hybridization studies on 42 stains presumptively identified as members of Flavobacterium group IIb and Flavobacterium breve indicated pronounced genotypic heterogeneity within these taxa. Three large groups highly related to the type strains of F. gleum, F. indologenes and F. breve respectively, and eight small groups were found. The group containing the type strain of F. breve was phenotypically indistinguishable from another genomic group, and these two groups were significantly separated from the other flavobacteria studied. The other nine genomic groups, representing Flavobacterium group IIb, could not with certainty be differentiated from each other by phenotypic characteristics, and there is no evidence indicating that these genomic groups differ from each other with respect to pathogenicity or ecology. Thus, it is suggested that for the time being the name "Flavobacterium group IIb" rather than specific epithets continue to be used for these bacteria.