Oral diseases are biofilm-mediated diseases caused by imbalances in the ecology of resident microflora. Among them, dental caries (tooth decay) is considered the most common disease worldwide, and toothbrushing, which physically eliminates the oral biofilm, is the most widespread prevention strategy. Although it is well established that fluoride increases enamel resistance to acidic pH and promotes tooth remineralization, its effect on the biofilm bacterial communities’ composition and metabolism is not fully understood. We have grown in vitro oral biofilms and used 16S rRNA Illumina sequencing to study the effect of fluoride on DNA- and RNA-based bacterial populations. In addition, a metatranscriptomic approach has also been performed, in which total RNA has been sequenced to study gene expression profiles in the presence/absence of 500 ppm sodium fluoride. Our data show a lower pH drop and a clear shift in total and metabolically active bacterial composition after fluoride exposure. Streptococcus oralis was the species most affected, with a 10-fold reduction in both DNA and RNA samples, whereas Rothia mucilaginosa underwent an 8-fold increase in the DNA and S. salivarius a 4- and 5-fold increase in the RNA and DNA samples, respectively. The metatranscriptomes indicated that fluoride exposure induced a dramatic shutdown of sugar metabolism, including significant under-expression of different sugar transporters, fucosidases, and a pyruvate oxidase, among others. The reduction in saccharolytic organisms and the inhibition of sugar fermentation pathways by fluoride may therefore be considered instrumental for the beneficial effect of fluoride-containing oral hygiene products.

口腔疾病是由常驻菌群生态失衡引起的生物膜介导的疾病。其中，龋齿（蛀牙）被认为是全世界最常见的疾病，而从物理上消除口腔生物膜的牙刷是最广泛的预防策略。尽管众所周知，氟化物可提高瓷釉对酸性pH的抵抗力并促进牙齿的再矿化，但其对生物膜细菌群落组成和新陈代谢的影响尚未完全了解。我们已经生长了体外口腔生物膜，并使用16S rRNA Illumina测序来研究氟化物对基于DNA和RNA的细菌种群的影响。此外，还进行了元转录组学方法，其中已对总RNA进行了测序，以研究是否存在500 ppm氟化钠时的基因表达谱。我们的数据显示，暴露于氟化物后，pH值降低得更低，总细菌和代谢活性细菌组成发生明显变化。口头链球菌是受影响最严重的物种，DNA和RNA样品均减少了10倍，而粘菌Rothia mucilaginosa的DNA增加了8倍，唾液链球菌的RNA和DNA则增加了4倍和5倍样本。元转录组表明，氟化物暴露引起糖代谢的显着停止，包括不同糖转运蛋白，岩藻糖苷酶和丙酮酸氧化酶的显着低表达。因此，可以认为糖酵解生物的减少和氟化物对糖发酵途径的抑制对于含氟化物的口腔卫生产品的有益作用是有帮助的。