Matsumi Y, Fujita K, Takashima Y, Yanagida K, Morikawa Y, Matsumoto-Nakano M
Department of Pediatric Dentistry, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.
Mol Oral Microbiol. 2015 Jun;30(3):217-26. doi: 10.1111/omi.12085. Epub 2014 Nov 10.
Glucan-binding proteins (Gbps) of Streptococcus mutans, a major pathogen of dental caries, mediate the binding of glucans synthesized from sucrose by the action of glucosyltransferases (GTFs) encoded by gtfB, gtfC, and gtfD. Several stress proteins, including DnaK and GroEL encoded by dnaK and groEL, are related to environmental stress tolerance. The contribution of Gbp expression to biofilm formation was analyzed by focusing on the expression levels of genes encoding GTFs and stress proteins. Biofilm-forming assays were performed using GbpA-, GbpB-, and GbpC-deficient mutant strains and the parental strain MT8148. The expression levels of gtfB, gtfC, gtfD, dnaK, and groEL were evaluated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Furthermore, the structure of biofilms formed by these Gbp-deficient mutant strains was observed using confocal laser scanning microscopy (CLSM). Biofilm-forming assay findings demonstrated that the amount formed by the GbpA-deficient mutant strain (AD1) was nearly the same as that by the parental strain, while the GbpB- and GbpC-deficient mutant strains produced lower amounts than MT8148. Furthermore, RT-qPCR assay results showed that the expressions of gtfB, dnaK, and groEL in AD1 were elevated compared with MT8148. CLSM also revealed that the structure of biofilm formed by AD1 was prominently different compared with that formed by the parental strain. These results suggest that a defect in GbpA influences the expression of genes controlling biofilm formation, indicating its importance as a protein for firm and stable biofilm formation.
变形链球菌是龋齿的主要致病菌，其葡聚糖结合蛋白（Gbps）介导由gtfB、gtfC和gtfD编码的葡糖基转移酶（GTFs）作用下从蔗糖合成的葡聚糖的结合。几种应激蛋白，包括由dnaK和groEL编码的DnaK和GroEL，与环境应激耐受性有关。通过关注编码GTFs和应激蛋白的基因表达水平，分析了Gbp表达对生物膜形成的贡献。使用GbpA、GbpB和GbpC缺陷突变株和亲本菌株MT8148进行生物膜形成试验。通过逆转录定量聚合酶链反应（RT-qPCR）评估gtfB、gtfC、gtfD、dnaK和groEL的表达水平。此外，使用共聚焦激光扫描显微镜（CLSM）观察这些Gbp缺陷突变株形成的生物膜结构。生物膜形成试验结果表明，GbpA缺陷突变株（AD1）形成的量与亲本菌株几乎相同，而GbpB和GbpC缺陷突变株产生的量低于MT8148。此外，RT-qPCR试验结果表明，与MT8148相比，AD1中gtfB、dnaK和groEL的表达升高。CLSM还显示，AD1形成的生物膜结构与亲本菌株形成的生物膜结构明显不同。这些结果表明，GbpA缺陷会影响控制生物膜形成的基因表达，表明其作为一种对牢固稳定生物膜形成至关重要的蛋白质的重要性。
