变形链球菌F-ATP酶亚基基因uncA遗传多态性的研究

目的研究变形链球菌临床分离株耐酸因子F—ATP酶亚基α的结构基因uncA的遗传多态性，并探讨基因多态性与细菌耐酸力及龋病发生的关系。方法分别从高龋、无龋个体中分离变形链球菌34和30株，其中包括18株高耐酸株、20株低耐酸株。从细菌组DNA扩增uncA，行限制性内切酶长度多态性分析（RFLP）及核酸测序比较。结果不同限制性内切酶RFLP产生不同的基因型，测序证实了导致多态出现的基因变异；内切酶Hph Ⅰ产生的A、B基因型在不同患龋个体分离菌株的分布不同（P〈0．05），A型uncA在高龋分离株的检出率高于无龋分离株；内切酶MboⅡ产生的C、D基因型在不同耐酸力菌株中的分布不同（P〈0．05），C型uncA在高耐酸力菌株的检出率高于低耐酸力菌株。结论变形链球菌F—ATP酶的α亚基基因uncA具有明显遗传多态性，酸性环境下生存力强的菌株可能出现基因的适应性变异，不同基因型uncA分布与菌株的耐酸力及致龋力相关。

Genetic diversity of F-ATPase subunits gene uncA amplified from Streptococcus mutans clinical isolates

OBJECTIVE: To study the genetic diversity of F-ATPase alpha subunit gene uncA derived from Streptococcus mutans (S. mutans) clinical isolates and to investigate the relationship between the genetic diversity of acidurance factor and S. mutans aciduric ability, also and the cariogenicity. METHODS: Sixty-four 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 was amplified with specific primers from S. mutans genomic DNA, then the PCR products were analyzed by RFLP and sequenced. RESULTS: Two genotypes A and B of PCR-RFLP were revealed when digested with Hph I. Mbo II also produced two different pattern C and D. 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 there existed variation of Hph I and Mbo II recognized sites. CONCLUSIONS: This study indicates that uncA gene of S. mutans F-ATPase obviously displayed genetic diversity. The different Hph I-RFLP and Mbo II-RFLP genotypes could be related to the cariogenicity and acid tolerance of S. mutans strains.