Genetic diversity within F-ATPase alpha subunit of Streptococcus mutans isolates

Objectives:The purpose of this research is to study the genetic diversity of F-ATPase alpha subunit gene uncA derived from Streptococcus mutans (S.mutans) clinical isolates, furthermore to investigate the relationships between the genetic diversity of acidurance factor and S.mutans aciduric ability, also and the cariogenicity. Methods: 64 S.mutans strains derived from 34 caries-active individuals and 30 caries-free individuals, including 18 strains displaying high acid tolerance and 20 strains displaying low acid tolerance. Gene uncA were amplified with specific primers from S.mutans genomic DNA, then the PCR products were analyzed by RFLP and sequenced. SPSS11.0 statistic software assayed the results. Results:It is testified that two genotypes A and B of PCR-RFLP were revealed when digested with Hph1. Mbo2 digested fragments of uncA were also shown two different pattern C and D. Pearson Chi-square 2-sided Test showed that the distributions of A and B genotype strains with different caries-sensitivity groups were different(P<0.05), and the proportion of A genotype strains from caries-activity group was higher than that from caries-free one. The distributions of C and D genotype strains with different acidurance strains were different(P<0.05), and the proportion of C genotype strains from high acid tolerance group was higher than that from low acid tolerance group. These amplified uncA genes from different group were sequenced and were testified that there existed variation of Hph1 and Mbo2 recognized sites. Conclusion:This study indicated that uncA gene of S.mutans F-ATPase obviously displayed genetic diversity. The different Hph1-RFLP and Mbo2-RFLP genotypes would be related to the cariogenicity and acid tolerance of S.mutans strains. This research was supported by NSFC 30171013 and Guizhou Nature Scientific Foundation of China (2004)3055.