Aims: Streptococcus mutans is highly sensitive to inhibitors of proton-pumping F-type ATPase (F-ATPase) under acidic conditions. Herein, we investigated the role of S. mutans F-ATPase in acid tolerance using a bacterium expressing the F-ATPase β subunit at lower levels than the wild-type strain.
Methods and results: We generated a mutant S. mutans expressing the catalytic β subunit of F-ATPase at lower levels than the wild-type bacterium. The mutant cells exhibited a significantly slower growth rate at pH 5.30, whereas the rate was essentially the same as that of wild-type cells at pH 7.40. In addition, the colony-forming ability of the mutant was decreased at pH <4.30 but not at pH 7.40. Thus, the growth rate and survival of S. mutans expressing low levels of the β subunit were reduced under acidic conditions.
Conclusions: Together with our previous observations, this study indicates that F-ATPase is involved in the acid tolerance mechanism of S. mutans by secreting protons from the cytoplasm.
Keywords: Streptococcus mutans; ATP synthase; F-ATPase; acid tolerance; dental caries; proton-pumping atpase.
© The Author(s) 2023. Published by Oxford University Press on behalf of Applied Microbiology International.