[Base composition of DNA from fluoride  resistant strains of streptococcus mutans and streptococcus sobrinus].
OBJECTIVE
To evaluate the genotype change of fluoride-resistant strains of S.mutans and S.sobrinus.


METHODS
High potential liquid chromatography was used to measure the base composition of DNA from F-resistant strains of S.mutans and S.sobrinus and their parent strains.


RESULTS
The data showed that the DNA G+C mol% of F-resistant and F-sensitive S.mutans were quite different, the difference was over 5%. The four F-resistant strains were 54.45, 44.86, 54.41, 55, 390, whereas the corresponding four parent strains were 35.38, 37.4, 43.35, 46.62, respectively.


CONCLUSIONS
The genotypes of F-resistant strains of S.mutans and S.sobrinus have been changed and may comprise several gene mutations.
School of Stomatology, Shanghai Second Medical University, Shanghai 200011, China.
J Y
JY
Sheng
Z
Z
Liu