Relationships among the oral fusobacteria assessed by DNA-DNA hybridization.

DNA was purified from 16 strains of Fusobacterium nucleatum and from five strains representing other Fusobacterium species. The relationships among fusobacteria were examined by DNA-DNA hybridization and by determining the guanine plus cytosine content of the DNA. F. nucleatum was found to comprise a heterogenous group of organisms related to Fusobacterium periodonticum and Fusobacterium simiae, but unrelated to any of the other species of Fusobacterium tested.