A Study on Genetic Diversity within Surface Protein of Streptococcus mutans

Objective: To study the relationship between genetic diversity within surface protein P1 of Streptococcus mutans serotype c and adherent abilities. Methods: Bacterial strains involved two groups, 44 S.mutans isolates with different adherent abilities, which were derived from previous work in our experimental lab. The bacterial DNA was extracted. The genes encoding A-region, P,V-region, C-terminus in surface protein P1, spaP-a(473-1571bp),spaP-pv(2060-3157bp),spaP-c(4003-4851bp) were amplified respectively by PCR. Genetic diversity were assessed by restriction fragment-length polymorphism(RFLP) with restriction endonucleases Hae¢ó and AluI. Sequence analysis of spaP-pv in 19 strains was performed. Results: 1. Four different patterns of spaP-a PCR-Hae¢ó and two genotypes of spaP-c PCR-AluI were revealed. The distribution of genotypes in strains with different adherent abilities was not different. 2. Two different genotypes(a, b) of spaP-pv were revealed when digested with AluI. The distribution of two genotypes in 44 strains with different adherent abilities was analysed with bilateral chi-square test and it had statistical significance(p<0.05). Sequence analysis of spaP-pv identified two different DNA fragments between a, b genotype strains and they were located in V-region of surface protein P1. Conclusion: It suggests that variation of gene encoding V-region may account for different adherent abilities of surface protein of S. mutans isolates. (The study is supported by grant from Chinese National Nature Science Fund 30171013.)