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附着并在牙齿表面形成生物膜，这使得病原体能够耐受快速而频繁的环境波动，如营养物质的可获得性、好氧到厌氧的转变和pH变化。对氨离子转运体的研究非常重要，因为它们在变形链球菌吸收生物膜中的营养物质方面起着至关重要的作用。本研究旨在鉴定变形链球菌中与枯草芽孢杆菌的氨离子转运蛋白基因同源的nrgA基因SMu1510。一株nrgA缺失突变株(NRGD)在氨离子存在下的生长速度低于亲本菌株。此外，激光共聚焦扫描显微镜显示，NRGD形成的生物膜与亲本菌株形成的生物膜结构有很大不同。这些结果表明，变形链球菌中的nrgA基因是分子输出和生物膜形成所必需的。

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.