Chloride channel permeases in Streptococcus mutans play a role in fluoride reisistance

Objectives: Fluoride has been widely applied for prevention of dental caries. The mechanisms are considered to be a strengthening of teeth and a promotion of tooth remineralization. In addition, the genome sequence of Streptococcus mutans predicts the presence of putative fluoride resistant proteins (called chloride channel permease). The purpose of the study is to evaluate the contribution of the chloride channel permease to fluoride resistance in S. mutans.
Methods: We used S. mutans UA159. We disrupted the genes (SMU1298c and SMU1289c), cording for chloride channel permeases. We transformed the SMU1298c or SMU1289c into a fluoride transporter-disrupted E.coli. We cultured each bacterial strain under the appropriate conditions with or without sodium halides.
Results: Although all the S. mutans strains were resistant for NaCl, NaBr and NaI, the gene-disrupted S.mutans strains were less resistant to NaF than wild type. SMU1298c or SMU1289c transformation rescued the fluoride transporter-disrupted E.coli from NaF toxicity.
Conclusions: We conclude that chloride channel permeases provide fluoride resistance to S.mutans.