title: Multilocus sequence analysis of Treponema denticola strains of diverse origin.
abstract: BACKGROUND
  The oral spirochete bacterium Treponema denticola is associated with both the incidence and severity of periodontal disease. Although the biological or phenotypic properties of a significant number of T. denticola isolates have been reported in the literature, their genetic diversity or phylogeny has never been systematically investigated. Here, we describe a multilocus sequence analysis (MLSA) of 20 of the most highly studied reference strains and clinical isolates of T. denticola; which were originally isolated from subgingival plaque samples taken from subjects from China, Japan, the Netherlands, Canada and the USA.
  
  
  RESULTS
  The sequences of the 16S ribosomal RNA gene, and 7 conserved protein-encoding genes (flaA, recA, pyrH, ppnK, dnaN, era and radC) were successfully determined for each strain. Sequence data was analyzed using a variety of bioinformatic and phylogenetic software tools. We found no evidence of positive selection or DNA recombination within the protein-encoding genes, where levels of intraspecific sequence polymorphism varied from 18.8% (flaA) to 8.9% (dnaN). Phylogenetic analysis of the concatenated protein-encoding gene sequence data (ca. 6,513 nucleotides for each strain) using Bayesian and maximum likelihood approaches indicated that the T. denticola strains were monophyletic, and formed 6 well-defined clades. All analyzed T. denticola strains appeared to have a genetic origin distinct from that of 'Treponema vincentii' or Treponema pallidum. No specific geographical relationships could be established; but several strains isolated from different continents appear to be closely related at the genetic level.
  
  
  CONCLUSIONS
  Our analyses indicate that previous biological and biophysical investigations have predominantly focused on a subset of T. denticola strains with a relatively narrow range of genetic diversity. Our methodology and results establish a genetic framework for the discrimination and phylogenetic analysis of T. denticola isolates, which will greatly assist future biological and epidemiological investigations involving this putative 'periodontopathogen'.
authors: Oral Biosciences, Faculty of Dentistry, The University of Hong Kong, Prince Philip Dental Hospital, 34 Hospital Road, Sai Ying Pun, Hong Kong.
authors: Sisu
authors: S
authors: Mo
authors: Meng
authors: M
authors: You
authors: Yvonne C F
authors: YC
authors: Su
authors: Donnabella C
authors: DC
authors: Lacap-Bugler
authors: Yong-biao
authors: YB
authors: Huo
authors: Gavin J D
authors: GJ
authors: Smith
authors: W Keung
authors: WK
authors: Leung
authors: Rory M
authors: RM
authors: Watt
mesh_terms: D001208:Asia; D001426:Bacterial Proteins / Q000235:genetics; D016000:Cluster Analysis; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D014644:Genetic Variation; D006801:Humans; D008969:Molecular Sequence Data; D058885:Multilocus Sequence Typing; D009426:Netherlands; D009656:North America; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D048373:Treponema denticola / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification
chemical_list: D001426:Bacterial Proteins; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S
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