Streptococcus periodonticum sp. nov., Isolated from Human Subgingival Dental Plaque of Periodontitis Lesion.

A novel facultative anaerobic and Gram-stain-positive coccus, designated strain ChDC F135, was isolated from human subgingival dental plaque of periodontitis lesion and was characterized by polyphasic taxonomic analysis. The 16S rRNA gene (16S rDNA) sequence of strain ChDC F135 was closest to that of Streptococcus sinensis HKU4 (98.2%), followed by Streptococcus intermedia SK54 (97.0%), Streptococcus constellatus NCTC11325 (96.0%), and Streptococcus anginosus NCTC 10713 (95.7%). In contrast, phylogenetic analysis based on the superoxide dismutase gene (sodA) and the RNA polymerase beta-subunit gene (rpoB) showed that the nucleotide sequence similarities of strain ChDC F135 were highly similar to the corresponding genes of S. anginosus NCTC 10713 (99.2% and 97.6%, respectively), S. constellatus NCTC11325 (87.8% and 91.4%, respectively), and S. intermedia SK54 (85.8% and 91.2%, respectively) rather than those of S. sinensis HKU4 (80.5% and 82.6%). The complete genome of strain ChDC F135 consisted of 1,901,251 bp and the G+C content was 38.9 mol %. Average nucleotide identity value between strain ChDC F135 and S. sinensis HKU4 or S. anginosus NCTC 10713 were 75.7% and 95.6%, respectively. The C composition of the cellular fatty acids of strain ChDC F135 (32.8%) was different from that of S. intermedia (6-8%), S. constellatus (6-13%), and S. anginosus (13-20%). Based on the results of phylogenetic and phenotypic analysis, strain ChDC F135 (= KCOM 2412 = JCM 33300) was classified as a type strain of a novel species of the genus Streptococcus, for which we proposed the name Streptococcus periodonticum sp. nov.