Genomic Insights Into the Treponema Genus: Taxonomic Resolution of Treponema vincentii and Description of Two Novel Species, Treponema plautii sp. nov. and Treponema sinense sp. nov.

Objectives: Periodontal disease, a global health concern, is strongly associated with oral treponemes. However, the taxonomy of some species remains unresolved, hindering our understanding of their roles in disease. This study aims to clarify the taxonomy of three strains isolated from patients with periodontal disease using phylogenomic and comparative genomic analyses.

Materials and methods: We performed genome sequencing for OMZ 800 and conducted phylogenomic and comparative genomic analyses of multiple strains to clarify their taxonomy.

Results: Phylogenomic and in-silico genome comparisons confirmed OMZ 800 as "T. vincentii" (Average Nucleotide Identity [ANI]>95%). We designated OMZ 800^T as the type strain for T. vincentii to establish its official standing in bacterial taxonomy. OMZ 806 (2.7 Mb, 44.9% GC) clustered with phylogroup IB strain (ANI>95% vs. OMZ 305), whereas OMZ 838 (2.7 Mb, 44.6% GC) clustered with phylogroup IA strains (ANI>95% vs. OMZ 855 and OMZ 857). Both OMZ 806 and OMZ 838 strains showed ANI<95% compared to T. medium ATCC700293^T, supporting their classification as novel species. We propose Treponema plautii sp. nov. OMZ 806^T (with OMZ305 as additional strain) and Treponema sinense sp. nov. OMZ 838^T (with OMZ 855 and OMZ 857 as additional strains).

Conclusion: This study clarifies Treponema taxonomy by designating OMZ 800^T as the type strain of T. vincentii and proposing two novel species, providing a refined taxonomical framework for this important genus.