HOMOLOGY AMONG TREPONEMA-DENTICOLA PLASMIDS

Three of 16 isolates of Treponema denticola were found to contain smal l (2.0-2.7 kb) cryptic plasmids. These were pTD1 from T. denticola ATC C 33520, pTD2 from strain T32A, and pTD3 from strain D3A1. These plasm ids were characterized by restriction mapping and cloned into E. coli plasmid pUC19. Extensive homology between these plasmids was revealed by Southern blot, and single-stranded DNA regions were found by neutra l Southern blots and S-1 nuclease mapping. These plasmids were not fou nd in serovars usually associated with human periodontal disease nor a re they universal in all T. denticola strains and serovars.