Author(s): Kang Di, Li Yuqing, Zhou Xuedong
Pages: 239-244
Year: 2017 Issue:  3
Journal: West China Journal of Stomatology
Keyword:  Streptococcus mutans; Streptococcus salivarius; green fluorescence protein; urease; promoter;
Abstract: Objective To construct a low-pH-sensing system inStreptococcus mutans (S. mutans) and to visually detect the pH in situ.Methods Promoter of ureaseⅠ(PureⅠ) and green fluorescence protein(gfp) DNA fragments were amplified by polymerase chain reaction (PCR) from the genome ofStreptococcus salivarius 57.I andS. mutans containing the gfp fragment. The two amplified DNA fragments were ligated together and further integrated into pDL278 to construct the recombinant plasmid pDL278-pureⅠ-gfp. This recombinant plasmid was then transformed intoS. mutans UA159 cells. Subsequently, the intensity of the optical density per unit area of the low-pH-sensing system was measured and compared under different pH conditions and different processing times.ResultsPureⅠ and gfp DNA fragments were amplified successfully with the correct molecule sizes (450 and 717 bp, respectively). The recombinant plasmid pDL278-pureⅠ-gfp was constructed and fur-ther verified by PCR and sequencing. The intensity of the optical density per unit area of the low-pH-sensing system increased with decreasing pH and increasing processing time.Conclusion A low-pH-sensing system was constructed successfully in S. mutans. Our research verified that pureⅠ ofStreptococcus salivarius can function well inS. mutans as an acid induced promoter, and provided a new method of detecting the pH of plaque biofilms in situ.