RELATIONSHIPS AMONG ACTINOMYCES-NAESLUNDII (A-VISCOSUS) BACTERIOPHAGES ISOLATED FROM SEWAGE AND THE ORAL CAVITY

Several lytic phages of Actinomyces naeslundii genospecies 2 (formerly A. viscosus) have been isolated from sewage and from dental plaque. T o define the relationships between these phages and ultimately to asse ss their role in the ecology of the human oral cavity, 13 phages isola ted from these two environments were purified and their biochemical pr operties compared. Five small, short-tailed phages, isolated from sewa ge over the course of several years (Av-1, Av-2, Av-3, 1281, and BF307 ) were morphologically indistinguishable from each other and from five phages recovered more recently from human dental plaque (CT1, CT2, CT 3, CT6 and CT7). The small phages (all morphotype C1) contained double -stranded linear DNA, 18 kb in size. In contrast, three phages from de ntal plaque (CT4, CT5 and CT8) possessed longer tails and much larger head structures (morphotype B1). Two of the larger phages (CT4 and CT5 ) contained DNA genomes estimated to be 80 kb in size, whereas large p hage CT8 contained DNA of approximately 50 kb. Restriction endonucleas e analysis revealed extensive differences between the large and small phages but the latter group showed similar, and in several cases ident ical, fragment patterns. These results indicate the existence of at le ast three distinct types of lytic bacteriophage active against oral Ac tinomyces spp. The similarities between the sewage and small dental pl aque isolates indicate a high degree of relatedness and suggest that t he sewage phages probably originated from the oral cavity.