Diversity of Treponema denticola and other oral treponeme lineages in subjects with periodontitis and gingivitis
More than 75 species/species-level phylotypes of taxa belonging to the genus Treponema inhabit the human oral cavity. Treponema denticola is commonly associated with periodontal disease, but the etiological roles and ecological distributions of other oral treponemes remain more obscure. Here, we compared the clinical distributions of phylogroup 1 and 2 oral treponemes in subgingival plaque sampled from Chinese subjects with periodontitis (n=10) and gingivitis (n=8), via the sequence analysis of the highly-conserved pyrH housekeeping gene. Two PCR primer sets that respectively targeted oral phylogroup 1 and 2 treponeme pyrH genes were used to construct plasmid clone-amplicon libraries for each subject, which were sequenced for bioinformatic analysis. 1,204 quality-filtered, full-length pyrH gene sequences were obtained from the cohort (median: 61.5; range: 59-83 of cloned pyrH sequences per subject), which were assigned to 34 pyrH genotypes (pyrH001-pyrH034; 97% sequence-identity cut-off). 18 pyrH genotypes (536 pyrH sequences) corresponded to phylogroup 1 treponeme taxa (including Treponema vincentii, Treponema medium). 16 pyrH genotypes (668 pyrH sequences) corresponded to T. denticola and other phylogroup 2 treponemes. Periodontitis subjects contained a greater diversity of phylogroup 2 pyrH genotypes, compared to gingivitis subjects (Mann-Whitney U-test). One T. denticola pyrH genotype (pyrH001) was highly prevalent: detected in 10/10 periodontitis and 6/8 gingivitis subjects. Several subjects harboured multiple T. denticola pyrH genotypes. Non-metric multidimensional scaling and PERMANOVA tests revealed no significant differences in overall pyrH genotype compositions between periodontitis and gingivitis subjects. In conclusion, our results clearly show that subjects with periodontitis and gingivitis commonly harbour highly-diverse oral treponeme communities.