DISTRIBUTION AND CHARACTERIZATION OF PLASMIDS IN ORAL ANAEROBIC SPIROCHETES

Fifteen oral spirochete strains belonging to the species Treponema den ticola, Treponema vencentii and Treponema socranskii as well as 9 fres h clinical isolates were screened for the presence of extrachromosomal plasmid DNA by a modified alkaline lysis procedure. A 2.6-kb plasmid was detected in both T. denticola ATCC 33520 and T. denticola e'. The 2.6-kb plasmid from T. denticola e' was shown to be similar to pTD1, p reviously reported by Ivic et al. in T. denticola ATCC 33520 on the ba sis of molecular weight, restriction endonuclease profile and DNA:DNA hybridization. T. denticola ATCC 33520 and T. denticola e' share 65% D NA homology and belong to different serological groups. This dissimila rity has been reconfirmed by specific immunofluorescence using polyclo nal and monoclonal antibodies. A plasmid-free T. denticola ATCC 33520 was identified. Comparative studies have shown no antigenic, morpholog ical, or genetic differences between the plasmid-bearing and the plasm id-free strain. In addition, screening of fresh clinical isolates of s pirochetes revealed the presence of a 4.2-kb plasmid in 4 of these str ains.