CHARACTERIZATION OF ACTINOMYCES WITH GENOMIC DNA FINGERPRINTS AND RIBOSOMAL-RNA GENE PROBES

Cellular DNA from 25 Actinomyces naeslundii and Actinomyces viscosus s trains belonging to the 7 taxonomic clusters of Fillery et al. (1978) and several unclustered strains was obtained by enzymatic and N-lauroy lsarcosine/guanidine isothiocyanate treatment of whole cells, followed by extraction of the nucleic acid. The DNA samples were digested with restriction endonucleases BamHI or PvuII, and agarose gel electrophor esis was used to obtain DNA fingerprints. The DNA fragments were subje cted to Southern blot hybridization with a digoxigenin-labeled cDNA pr obe transcribed from Escherichia coli 16S and 23S rRNA. The patterns o f bands from genomic (DNA fingerprints) and rDNA fingerprints (ribotyp es) were used for comparison between the taxonomic cluster strains and strains within clusters. Representative strains from each taxonomic c luster provided different BamHI DNA fingerprints and ribotype patterns with 3 to 9 distinct bands. Some strains within a cluster showed iden tical ribotype patterns with both endonucleases (A. naeslundii B120 an d A. naeslundii B102 from cluster 3), while others showed the same pat tern with BamHI but a different pattern with PvuII (A. naeslundii ATCC 12104 and 398A from cluster 5). A. viscosus ATCC 15987 (cluster 7) an d its parent strain T6 yielded identical fingerprint and ribotype patt erns. The genomic diversity revealed by DNA fingerprinting and ribotyp ing demonstrates that these techniques, which do not require phenotypi c expression, are suited for study of the oral ecology of the Actinomy ces, and for epidemiological tracking of specific Actinomyces strains associated with caries lesions and sites of periodontal destruction.