FF-ATPase Contributes to the Fluoride Tolerance and Cariogenicity of .

The phenotypic traits of , such as fluoride tolerance, are usually associated with genotypic alterations. The aim of this study was to identify adaptive mutations of to gradient fluoride concentrations and possible relationships between the mutations and fluoride tolerance. We identified a highly resistant strain (FR1000) with a novel single nucleotide polymorphism (SNP, -36G→T) in the promoter region of FF-ATPase gene cluster () resistant to 1,000 ppm fluoride using the whole-genome Illumina PE250 sequencing. Thus, a -36G→T FF-ATPase promoter mutation from the parental strain UA159 was constructed and named UA159-T. qRT-PCR showed that the FF-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 FF-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 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 FF-ATPase gene drastically contributed to the fluoride tolerance and enhanced cariogenicity of . These findings provided new insights into the mechanism of microbial fluoride tolerance, and suggested FF-ATPase as a potential target for suppressing fluoride resistant strains.