Fujian Key Laboratory of Oral Diseases &, Fujian Provincial Engineering Research Center of Oral Biomaterial & Stomatological Key lab of Fujian College and University, School and Hospital of Stomatology, Fujian Medical University, Fuzhou, China.
Stomatological Hospital, Southern Medical University, Guangzhou, China.
Mol Oral Microbiol. 2021 Aug;36(4):233-242. doi: 10.1111/omi.12344. Epub 2021 Jun 7.
The D-alanylation of lipoteichoic acid (LTA) is essential for the physiological metabolism of Streptococcus mutans (S. mutans). This study was designed to investigate the influence of D-alanylation of LTA on interspecies competitiveness of S. mutans.
The process of D-alanylation was blocked by the inactivation of dltC. Agar competition assays, conditioned medium assays, and qRT-PCR were used to evaluate the production of antimicrobial compounds in S. mutans mutant. Dual-species biofilm was formed to investigate the competitiveness of S. mutans mutant cocultured with S. sanguinis or S. gordonii.
S. mutans mutant could not produce antimicrobial compounds efficiently when cocultured with commensal bacteria (*p < 0.05). The mutant showed compromised competitiveness in dual-species biofilms. The ratio of the mutant in dual-species biofilms decreased, and the terminal pH of the culture medium in mutant groups (mutant+S. sanguinis/S. gordonii) was higher than that in wild-type groups (*p < 0.05). Scanning electron microscope (SEM) showed weaker demineralization of enamel treated with dual-species biofilms consisting of mutant and commensal bacteria.
D-Alanylation is involved in interspecies competitiveness of S. mutans within oral biofilm by regulating mutacins and lactic acid production, which may modulate the profiles of dental biofilms. Results provide new insights into dental caries prevention and treatment.
脂磷壁酸（LTA）的 D-丙氨酸化对于变形链球菌（S. mutans）的生理代谢至关重要。本研究旨在探讨 LTA 的 D-丙氨酸化对变形链球菌种间竞争力的影响。
通过失活 dltC 来阻断 D-丙氨酸化过程。采用琼脂竞争试验、条件培养基试验和 qRT-PCR 来评估 S. mutans 突变体产生抗菌化合物的情况。形成双物种生物膜，以研究 S. mutans 突变体与 S. sanguinis 或 S. gordonii 共培养时的竞争力。
当与共生菌共培养时，S. mutans 突变体不能有效地产生抗菌化合物（*p < 0.05）。突变体在双物种生物膜中表现出竞争劣势。双物种生物膜中突变体的比例降低，且突变体组（突变体+S. sanguinis/S. gordonii）的培养基终点 pH 值高于野生型组（*p < 0.05）。扫描电子显微镜（SEM）显示，用含有突变体和共生菌的双物种生物膜处理后，牙釉质的脱矿作用减弱。
D-丙氨酸化通过调节 mutacins 和乳酸的产生参与了口腔生物膜中 S. mutans 的种间竞争力，这可能调节了牙生物膜的特征。结果为龋齿的预防和治疗提供了新的见解。
