Whole Genome Shotgun sequencing of the Streptococcus sp. str CECT 7746 isolated from human caries-free tooth surface.. Streptococcus oralis subsp. dentisani 7746

Two Streptococci species were isolated from tooth surface of people who never have had caries. These isolates have specific growth inhibition on the Streptococcus mutans species. With the aim to detect the specific molecular pathway to inhibit the growth of S. mutans, we decided to sequence the entire genome of these isolates. Preliminary 16S rDNA based phylogeny demonstrated close relationship with S. oralis and S. mitis species. Genome wide comparisons using Average Nucleotide Identity (ANI) has shown DNA signature from Streptococcal species but significantly differ from S. oralis and S. mitis. Therefore, this evidences that both Streptococcus sp. str CECT 7746 and CECT 7747 are new Streptococcus species with potential usage as probiotic for human oral health.

本研究从无龋病个体的牙齿表面分离得到两株链球菌属（Streptococcus）物种。这两株分离株对变形链球菌（Streptococcus mutans）具有特异性生长抑制作用。为探究抑制变形链球菌生长的特异性分子通路，本研究决定对这两株分离株进行全基因组测序。基于16S rDNA的初步系统发育分析显示，二者与口腔链球菌（Streptococcus oralis）和轻型链球菌（Streptococcus mitis）亲缘关系密切。通过平均核苷酸同源性（Average Nucleotide Identity，ANI）开展的全基因组比较分析表明，其具备链球菌属的DNA特征，但与口腔链球菌和轻型链球菌存在显著差异。综上，本研究证实菌株CECT 7746与CECT 7747均为全新的链球菌属物种，具备作为人类口腔健康益生菌的应用潜力。