[Construction of a virulence-related gene library of Streptococcus mutans by suppression subtractive hybridization].
OBJECTIVE
To construct a suppression subtractive library of virulence-related genes from c serotype Streptococcus mutans (S. mutans), and lay foundations for screening the virulent genes.


METHODS
After being isolated from virulent and avirulent strain of S. mutans respectively, the intact and high-pure genomic DNA was digested with three appropriate four-base-cutting restriction endonueleases to produce fragments of optimal length. The digested DNA of the virulent strain ligated with adaptor was used as tester DNA, and that of the avirulent strain as driver DNA. Then the suppression subtractive hybridization was carried out, and the efficiency of ligation and subtraction detected respectively. The subtracted fragments were inserted into vector pCR2. 1 using T/A cloning kit, and transformed into E. coli TOP10F' competent cells. Those white colonies were selected to construct the suppression subtractive library.


RESULTS
Alu I chosen from three restriction endonucleases was verified to be suitable for preparing restriction fragments from S. mutans genomic DNA. Through electrophoresis of Alu I -digested DNA, a smear ranged from 0.1 to 2.0 kb was observed. The ligation efficiency of tester DNA with adaptor was at least higher than 25 percent. The subtraction efficiency of suppression subtractive hybridization confirmed the success in enrichment of differential genes between virulent and avirulent strain of S. mutans. In the subtracted group, the appearance time of the 23S rRNA gene both in tester and driver DNA was later than that in the unsubtracted group by six cycles. It suggested that suppression subtractive hybridization happened indeed. After the subtracted fragments were cloned, 96 colonies were picked up for constructing the suppression subtractive library of virulence-related genes of S. mutans.


CONCLUSIONS
Suppression subtractive hybridization allows rapid and easy construction of virulence-related gene library of S. mutans.
Guo
Li-hong
LH
Dept of Biology, College of Stomatology, Peking University, Beijing, China.
Shi
Jun-nan
JN
Zhang
Ying
Y
D004926:Escherichia coli; D015723:Gene Library; D009693:Nucleic Acid Hybridization; D013295:Streptococcus mutans; D066251:Subtractive Hybridization Techniques; D014774:Virulence