AUTHOR=Li Cheng , Qi Cai , Yang Sirui , Li Zhengyi , Ren Biao , Li Jiyao , Zhou Xuedong , Cai Huawei , Xu Xin , Peng Xian 

TITLE=F0F1-ATPase Contributes to the Fluoride Tolerance and Cariogenicity of Streptococcus mutans

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.777504

DOI=10.3389/fmicb.2021.777504

ISSN=1664-302X

ABSTRACT=<p>The phenotypic traits of <italic>Streptococcus mutans</italic>, such as fluoride tolerance, are usually associated with genotypic alterations. The aim of this study was to identify adaptive mutations of <italic>S. mutans</italic> to gradient fluoride concentrations and possible relationships between the mutations and fluoride tolerance. We identified a highly resistant <italic>S. mutans</italic> strain (FR1000) with a novel single nucleotide polymorphism (SNP, −36G→T) in the promoter region of F<sub>0</sub>F<sub>1</sub>-ATPase gene cluster (<italic>SMU_1527-SMU_1534</italic>) resistant to 1,000 ppm fluoride using the whole-genome Illumina PE250 sequencing. Thus, a −36G→T F<sub>0</sub>F<sub>1</sub>-ATPase promoter mutation from the parental strain <italic>S. mutans</italic> UA159 was constructed and named UA159-T. qRT-PCR showed that the F<sub>0</sub>F<sub>1</sub>-ATPase gene expression of both FR1000 and UA159-T was up-regulated, and fluoride tolerance of UA159-T was significantly improved. Complementation of Dicyclohexylcarbodiimide (DCCD), a specific inhibitor of F<sub>0</sub>F<sub>1</sub>-ATPase, increased fluoride susceptibility of FR1000 and UA159-T. Intracellular fluoride concentrations of fluoride tolerance strains were higher compared to UA159 strain as demonstrated by <sup>18</sup>F analysis. Further validation with rat caries models showed that UA159-T caused more severe caries lesions under fluoride exposure compared with its parental UA159 strain. Overall, the identified −36G→T mutation in the promoter region of F<sub>0</sub>F<sub>1</sub>-ATPase gene drastically contributed to the fluoride tolerance and enhanced cariogenicity of <italic>S. mutans</italic>. These findings provided new insights into the mechanism of microbial fluoride tolerance, and suggested F<sub>0</sub>F<sub>1</sub>-ATPase as a potential target for suppressing fluoride resistant strains.</p>