Description of Streptococcus dentalis sp. nov., Streptococcus gingivalis sp. nov., and Streptococcus lingualis sp. nov., Isolated from Human Oral Cavities

We isolated three novel strains, S1 T , S2 T , and S5 T , from human oral cavities and identified them as distinct novel species. All these strains are facultatively anaerobic, Gram-stain-positive, and non-flagellated bacteria. Their optimal growth conditions for these strains were observed in Columbia broth (CB) at 37 °C, pH 7.0, and in the absence of NaCl. Phylogenetic analyses, employing the 16S rRNA gene and whole-genome sequencing, confirmed that all three strains belong to the genus Streptococcus . The 16S rRNA gene sequences of strains S1 T , S2 T , and S5 T showed the highest similarities to Streptococcus parasanguinis , 98.57%, 99.05%, and 99.05%, respectively, and the orthologous average nucleotide identity (OrthoANI) values between the three strains and S. parasanguinis were 93.82%, 93.67%, and 94.04%, respectively. The pairwise OrthoANI values between the novel strains were 94.37% (S1 T –S2 T ), 95.03% (S2 T –S5 T ), and 94.71% (S1 T –S5 T ). All strains had C 20:1 ω 9 c and summed feature 8 (C 18:1 ω 7 c and/or C 18:1 ω 6 c ) as major cellular fatty acids. Additionally, diphosphatidylglycerol (DPG) and hydroxyphosphatidylethanolamine (OH-PE) were identified as major polar lipids. Menaquinone was undetected in all strains. The results from the phylogenetic, phenotypic, chemotaxonomic, and genotypic analyses collectively indicated that strains S1 T , S2 T , and S5 T represent three distinct novel species within the genus Streptococcus , and we propose the names Streptococcus dentalis sp. nov. for strain S1 T (= KCTC 21234 T = JCM 36526 T ), Streptococcus gingivalis sp. nov. for strain S2 T (= KCTC 21235 T = JCM 36527 T ), and Streptococcus lingualis sp. nov. for strain S5 T (= KCTC 21236 T = JCM 36528 T ).