Wang Rui, Wang Yigan, Lei Zixue, Hao Liying, Jiang Li
State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, People's Republic of China.
Microbiol Immunol. 2022 Nov;66(11):493-500. doi: 10.1111/1348-0421.13025. Epub 2022 Sep 29.
Biofilm on dental restorative materials is an important determinant in the etiology of secondary caries development. Formation of biofilm involves adhesion of bacteria onto substrate, bacterial cell, and biofilm surfaces. Glucosyltransferase B and C (GtfB and GtfC) are essential factors for regulation of Streptococcus mutans biofilm formation, but the mechanisms involving different kinds of bacterial adhesion still lack detailed description. In this study, nanoscale adhesion force measurement was performed using atomic force microscopy. Bacteria-coated cantilevers were used to probe S. mutans adhesion to substrates, bacterial cells, and early biofilms. Two representative dental materials, glass ionomer cement (GIC) and composite resin, served as substrates. It was found that deletion of gtfB and gtfC genes both reduced adhesion forces of S. mutans toward substrate and bacterial cell surfaces (P < 0.05). Notably, reduction of the gtfB gene remarkably decreased bacterial adhesion to biofilm surfaces (P < 0.05), while gtfC showed no obvious effect during this stage. Biofilms cultured on GIG further decreased cell-biofilm adhesion, compared with those on resin (P < 0.05). Confocal fluorescence images and scanning electron microscopy images showed that deletion of gtfB lead to reduced microcolony formation and less production of exopolysaccharides (EPSs) in the biofilm, and after bacterial culturing on GIC, the EPS content was further decreased. Our findings suggest that EPSs mainly mediate bacterial adhesion to early biofilm surface. Deletion of gtfB and coculture with GIC could significantly reduce the cell-biofilm adhesion, which is probably through decreasing of EPS production. gtfB exerts a critical role in the bacterial adhesion for the whole process of biofilm development, while gtfC possibly works only in the early stages.
牙科修复材料上的生物膜是继发龋发展病因中的一个重要决定因素。生物膜的形成涉及细菌在底物、细菌细胞和生物膜表面的黏附。葡糖基转移酶B和C（GtfB和GtfC）是变形链球菌生物膜形成调控的关键因素，但涉及不同类型细菌黏附的机制仍缺乏详细描述。在本研究中，使用原子力显微镜进行了纳米级黏附力测量。用细菌包被的悬臂探针检测变形链球菌对底物、细菌细胞和早期生物膜的黏附。两种代表性的牙科材料，玻璃离子水门汀（GIC）和复合树脂，用作底物。研究发现，gtfB和gtfC基因的缺失均降低了变形链球菌对底物和细菌细胞表面的黏附力（P < 0.05）。值得注意的是，gtfB基因的缺失显著降低了细菌对生物膜表面的黏附（P < 0.05），而gtfC在此阶段没有明显影响。与在树脂上培养的生物膜相比，在GIG上培养的生物膜进一步降低了细胞与生物膜的黏附（P < 0.05）。共聚焦荧光图像和扫描电子显微镜图像显示，gtfB的缺失导致生物膜中微菌落形成减少和胞外多糖（EPSs）产生减少，并且在GIC上培养细菌后，EPS含量进一步降低。我们的研究结果表明，EPSs主要介导细菌对早期生物膜表面的黏附。gtfB的缺失以及与GIC共培养可显著降低细胞与生物膜的黏附，这可能是通过减少EPS的产生实现的。gtfB在生物膜发育的整个过程中对细菌黏附起着关键作用，而gtfC可能仅在早期阶段起作用。
