Streptococcus mutans transcriptome in the presence of sodium fluoride and sucrose

Objective: Considering the diverse mechanisms by which fluoride could affect oral bacteria, this study evaluated the effect of sodium fluoride onStreptococcus mutans transcriptome in the presence of sucrose. Methods: S. mutans UA159 was cultured in 3 different types of media: medium control[TY], sucrose control [TY_S], and sodium fluoride sucrose test[TY_S_NaF]. Triplicates of each group were sampled at exponential phase 3 h after inoculation, total RNA was isolated, mRNA enriched and cDNA paired-end sequenced (Illumina Hi-Seq2500). Results: Genes related toS. mutans adhesion(gtf13 and gtfC), acidogenicity and sugar transport were up-regulated in the presence of sucrose(TY_S) and sucrose/fluoride(TY_SNaF), whereas gene dItA, D-alanine-activating enzyme, which is related to regulation of non-PTS sugar internalization was down-regulated. Up-regulation of the scrA gene and the PTS fructose-and mannose system, as well as functions such as those involved in stress and defence responses and peptidases; and down-regulation of lacACDG and pyruvate formate-lyase were observed in the TY_S _NaF group, as compared to TY_S group. Conclusions: The presence of NaF has decreased the overall gene expression level inS. mutans. However, its major effect seems to be the inducing of expression of genes involved in some PEP:PTS systems and other metabolic transporters which imply specific cellular internalisation of sugars.