DEOXYRIBONUCLEIC-ACID HYBRIDIZATION AMONG STRAINS OF ACTINOMYCES-VISCOUSUS AND ACTINOMYCES-NAESLUNDII

DNAs were extracted from strains of A. viscosus and A. naeslundii and were compared by DNA-DNA hybridization. When their DNAs were compared by hybridization on membrane filters, A. viscosus strains from humans were barely separable from A. naeslundii strains, but A. viscosus strains from hamsters were distinctly different. A. viscosus strains from veterinary infections were identical to human strains. With the use of the more sensitive S1 nuclease hybridization method with DNA from a set of strains that had been used in a numerical taxonomy study, typical A. viscosus strains from humans could be distinguished from typical A. naeslundii strains. A group of atypical A. naeslundii strains could also be delineated. The results generally parallel the taxonomic divisions of these organisms based on serology or numerical taxonomy. A. viscosus strains from humans and A. naeslundii strains are similar but distinguishable, but A. viscosus strains from hamsters are clearly separable.