Functional analysis of signal transduction system involving membrane transporters in Streptococcus mutans

变形链球菌代谢碳水化合物以粘附和形成牙齿表面的生物膜，这使得病原体能够忍受快速和频繁的环境波动，如营养物质的可用性、好氧到厌氧的转变和pH值的变化。铵转运体的研究是重要的，因为它们在生物膜中变形链球菌对营养物质的吸收中起着至关重要的作用。本研究主要对S. mutans中与nrgA对应的SMu1510基因进行了表征，该基因与枯草芽孢杆菌中的铵转运体基因同源。在铵的存在下，nrga缺陷突变株（NRGD）的生长速度低于亲本菌株。此外，共聚焦激光扫描显微镜显示，NRGD形成的生物膜结构与亲本菌株形成的生物膜结构有很大不同。这些结果表明，nrgA基因在突变链球菌的分子输出和生物膜的形成中是必不可少的。

Streptococcus mutans metabolizes carbohydrates for adherence to and formation of biofilm on tooth surfaces, which allows the pathogen to tolerate rapid and frequent environmental fluctuations, such as nutrient availability, aerobic-to-anaerobic transitions, and pH changes. Investigation of ammonium transporters is important, as they play crucial roles in the uptake of nutrients by S. mutans in biofilm. The present study focused on characterizing the SMu1510 gene corresponding to nrgA in S. mutans, which is homologous to the ammonium transporter gene in Bacillus subtilis. The growth rate of an nrgA-deficient mutant strain (NRGD) was lower than that of the parental strain in the presence of ammonium. In addition, confocal laser scanning microscopy revealed that the structure of biofilm formed by NRGD was drastically different as compared to formed by the parental strain. These results suggest that the nrgA gene in S. mutans is essential for export of molecules and biofilm formation.