RpoB and DnaK Sequences of Unidentified Veillonella Isolates

Objectives: Currently, the genus Veillonella is subdivided into 13 species. Of these species, only V. atypica, V. denticariosi, V. dispar, V. parvula, V. rogosae and V. tobetsuensis have been isolated from human oral cavities as oral Veillonella. In our previous study, 1609 strains of genus Veillonella were isolated from the saliva of children. Among these 1609 isolates, 167 isolates (10.4%) could not be identified as belonging to the 6 oral Veillonella species, and were suggested to be member of one or more novel Veillonella species. Therefore, the objective of this study was to analyze the phylogenetics of the unidentified isolates based on rpoB and dnaK gene sequences to establish the novel species of genus Veillonella.
Methods: As the representative of the unidentified isolates, 24 isolates were chosen in this study. The PCR-based amplification and sequence analysis of rpoB and dnaK were performed by using the previously described primers. The sequences are determined with an ABI PRISM 310 Genetic Analyzer. The rpoB (495-632nt) and dnaK (543-607nt) partial sequences of these isolates were aligned against the sequences of the representative strains retrieved from GenBank. BLAST search, pairwise similarity values and construction of phylogenetic tree were studied by using LASERGENE program (DNASTAR).
Results: In the phylogenetic tree of rpoB and dnaK gene, these unidentified isolates formed distinct cluster within the established species of genus Veillonella. The intraspecific similarities of these unidentified isolates were varied between 94.3% and 100% of the rpoB and dnaK gene sequences, respectively. Meanwhile, the pairwise similarity of these isolates showed less than 93% level of rpoB and dnaK against the established species of genus Veillonella.
Conclusions: These results strongly indicated the possibility of some novel species of the genus Veillonella.