Objective To study the genetic diversity and the gene expression of membrane- bound proton- translocating ATPase（F- ATPase） subunit gene uncG derived from Streptococcus mutans（S.mutans） clinical isolates. Methods 38 S.mutans strains derived from caries- active and caries- free individuals including 18 strains displaying high acid tolerance and 20 strains displaying low acid tolerance. Gene uncG was amplified with specific primers from S.mutans genomic DNA, then the PCR product was analyzed by RFLP and sequenced. The relative expression quantity of uncG gene against the housekeeping gene recA was determined by using RT- PCR method. A gel documentation system and QUANTITY ONES software were used to analyze the data results. Results It was testified that four genotypes A, B, C and D of PCR- RFLP were revealed when respectively digested with AluⅠ and BsrⅠ , but the distributions of the four genotype strains showed no difference（P >0.05）. The differences of uncG gene transcript quantities derived from different genotype or different aciduranc strains had no significance（P>0.05）. Conclusion This study indicated that uncG gene of F- ATPase obviously displayed genetic diversity and existed polymorphism at mRNA expression level, while the AluⅠ- RFLP genotypes and the expression levels would not be responsive to different acid tolerance of S.mutans strains.
