[A comparison of the activities of membrane-bound, proton translocating ATPases between Streptococcus mutans fluoride-resistant and their parent strains].
OBJECTIVE
To figure out the reason for increased acid tolerance of Ingbritt-FR, the fluoride-resistant strain of Streptococcus mutans Ingbritt, by determining and comparing the H(+)-ATPase activities of both fluoride-resistant and their parental strains.


METHODS
The permeabilized cells of S. mutans Ingbritt and Ingbritt-FR were prepared by treating them with 10% toluene and then two cycles of freezing and thawing. The permeabilized cells were used for ATPase assay by adding them to the reaction mixture which contained 50mM Tris-maleate buffer (pH 6.0), 10 mM MgSO4 and 5 mM ATP. ATPase activity was assessed by measuring inorganic phosphate released from ATP hydrolysis.Two-way ANOVA was used for statistical analysis.


RESULTS
The activities of H(+)-ATPase of Ingbritt-FR were 308.48, 136.67, and 82.80 micromol Pi/g cell dry weight/min, at 10, 20, and 60 minutes respectively, significantly higher than those of their parent strain: 104.77, 64.69, and 30.7 (P<0.01). The enzyme activities were decreasing with time.


CONCLUSIONS
The higher ATPase activity of fluoride-resistant mutant of S. mutans Ingbritt may account for the increased acid tolerance of this organism, and the increment of ATPase activity and acid tolerance of fluoride-resistant strain is likely to increase the cariogenic potential of S. mutans after fluoride-resistant mutation.
Sheng
Jiang-Yun
JY
Department of Endodontics, Ninth People's Hospital, School of Stomatology, Shanghai Second Medical University.Shanghai 200011, China. sris@sh163.com
Huang
Zheng-Wei
ZW
Liu
Zheng
Z
D000143:Acids / Q000737:chemistry; D001426:Bacterial Proteins / Q000378:metabolism*; D024881:Drug Resistance, Bacterial; D005459:Fluorides / Q000494:pharmacology*; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D013295:Streptococcus mutans / Q000187:drug effects / Q000201:enzymology*
D000143:Acids; D001426:Bacterial Proteins; D006180:Proton-Translocating ATPases; D005459:Fluorides