Plasmid content of some oral microorganisms isolated from subgingival plaque.

Eighty-five strains of bacterial species selected from the predominant cultivable dental plaque flora of patients with different periodontal pathologies were examined for their plasmid content. Microorganisms studied included: Actinomyces viscosus, A. odontolyticus, Bacteroides asaccharolyticus (B. gingivalis), B. melaninogenicus subspecies intermedius, and subspecies melaninogenicus, Capnocytophaga ochracea (B. ochraceus), and Fusobacterium nucleatum. Three B. melaninogenicus isolates showed plasmids of approximately 2.7-2.9 Mdalton (mega-dalton) molecular size. Restriction enzyme digests of the plasmids demonstrated dissimilar patterns when electrophoresed on agarose gels. In other microorganisms, including the Actinomyces species, plasmids were not observed.