Department of Cardiology and Endodontology & National Clinical Research Center for Oral Disease, School and Hospital of Stomatology, Peking University, Beijing, P. R. China.
Department of Geriatric Dentistry, School and Hospital of Stomatology, Peking University, Beijing, P. R. China.
Mol Oral Microbiol. 2022 Jun;37(3):97-108. doi: 10.1111/omi.12364. Epub 2022 Mar 13.
The acid tolerance of Streptococcus mutans plays an important role in its cariogenic process. Streptococcus mutans initiates a powerful transcriptional and physiological adaptation mechanism, eventually shielding the cellular machinery from acid damage and contributing to bacterial survival under acidic stress conditions. Although S. mutans contains complex regulatory systems, existing studies have shown that S. mutans, unlike Escherichia coli, cannot maintain a neutral intracellular environment. As the pH of the extracellular environment decreases, the intracellular pH decreases in parallel. There is insufficient knowledge regarding the acid resistance of the intracellular proteins of S. mutans, particularly when it comes to the key cytoskeletal division protein FtsZ. In this study, the data showed that S. mutans had similar cell division progress in acidic and neutral environments. The splitting position was in the middle of cells, and the cytoplasm was divided evenly in the acidic environment. Additionally, the tread milling velocity of S. mutans FtsZ in the middle of cells was not affected by the acidic environment. Streptococcus mutans FtsZ had higher GTPase activity in pH 6.0 buffer than in the neutral environment. Furthermore, the polymerization of S. mutans FtsZ in the acidic environment was more robust than that in the neutral environment. After two particular amino acids of S. mutans, FtsZ amino acids were mutated (E88K, L269K), the polymerization of S. mutans FtsZ in the acidic environment was significantly reduced. Overall, S. mutans FtsZ exhibited higher functional activity in pH 6.0 buffer in vitro. The acid resistance of S. mutans FtsZ is affected by its particular amino acids.
变形链球菌的耐酸性在其致龋过程中起着重要作用。变形链球菌启动了强大的转录和生理适应机制，最终使细胞机制免受酸的损伤，并有助于细菌在酸性应激条件下存活。尽管变形链球菌含有复杂的调控系统，但现有研究表明，与大肠杆菌不同，变形链球菌不能维持中性的细胞内环境。随着细胞外环境 pH 值的降低，细胞内 pH 值也随之降低。目前对于变形链球菌细胞内蛋白的耐酸性知之甚少，特别是对于关键的细胞骨架分裂蛋白 FtsZ 更是如此。在这项研究中，数据表明变形链球菌在酸性和中性环境中具有相似的细胞分裂进程。分裂位置在细胞中部，细胞质在酸性环境中均匀分裂。此外，变形链球菌 FtsZ 在细胞中部的 tread milling 速度不受酸性环境的影响。变形链球菌 FtsZ 在 pH6.0 缓冲液中的 GTPase 活性高于中性环境。此外，变形链球菌 FtsZ 在酸性环境中的聚合比中性环境更稳定。在两个特定的变形链球菌 FtsZ 氨基酸（E88K，L269K）发生突变后，变形链球菌 FtsZ 在酸性环境中的聚合明显减少。总的来说，变形链球菌 FtsZ 在体外 pH6.0 缓冲液中表现出更高的功能活性。变形链球菌 FtsZ 的耐酸性受其特定氨基酸的影响。
