J Korean Acad Oral Health.  2016 Dec;40(4):255-260. 10.11149/jkaoh.2016.40.4.255.

The pH-dependent effects of combining ethanol with fluoride on proton permeability in Streptococcus mutans

  • 1Department of Oral Biochemistry & Molecular Biology, School of Dentistry, Pusan National University, Yangsan, Korea. jsokang@pusan.ac.kr
  • 2Department of Preventive & Community Dentistry, School of Dentistry, Pusan National University, Yangsan, Korea.
  • 3BK21 PLUS Project, School of Dentistry, Pusan National University, Yangsan, Korea.


The aim of this research was to determine the pH-dependent changes in F-ATPase activity and proton fluxes in Streptococcus mutans (S. mutans) as induced by varying the concentration of fluoride ±10 mM (0.058% (v/v)) ethanol.
S. mutans UA159 was grown in Brain Heart Infusion medium at pH 4.8, 6.8, or 8.8. The F-ATPase assay was initiated by the addition of ATP, and stopped by adding 10% trichloroacetic acid. For the proton flux assay, bacterial suspensions were titrated to pH 4.6 with 0.5 M HCl, and then 0.5 M HCl was added to decrease the pH values in units of approximately 0.4 pH. The subsequent increase in pH was monitored using a glass electrode. To disrupt the cell membrane, 10% (v/v) butanol was added to the suspensions after 80 minutes.
At all pH levels, fluoride ±10 mM ethanol not only decreased F-ATPase activity but also increased the proton permeability of S. mutans. The largest effects were observed at pH 4.8. Ethanol enhanced these effects only at pH 4.8.
A very low concentration of ethanol enhanced the action of fluoride on F-ATPase activity and the proton permeability in S. mutans at acidic pH levels. We expect that low concentrations of ethanol may be used together with fluoride and/or other anticaries agents to develop more effective anticaries preparations.


ethanol; F-ATPase; Fluoride; pH stress; proton permeability; Streptococcus mutans
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