Nicotine Enhances Interspecies Relationship betweenStreptococcus mutansandCandida albicans
Streptococcus mutansandCandida albicansare common microorganisms in the human oral cavity. The synergistic relationship between these two species has been deeply explored in many studies. In the present study, the effect of alkaloid nicotine on the interspecies betweenS. mutansandC. albicansis explored. We developed a dual-species biofilm model and studied biofilm biomass, biofilm structure, synthesis of extracellular polysaccharides (EPS), and expression of glucosyltransferases (Gtfs). Biofilm formation and bacterial and fungal cell numbers in dual-species biofilms increased in the presence of nicotine. MoreC. albicanscells were present in the dual-species biofilms in the nicotine-treated groups as determined by scanning electron microscopy. The synthesis of EPS was increased by 1 mg/ml of nicotine as detected by confocal laser scanning microscopy. The result of qRT-PCR showedgtfsexpression was upregulated when 1 mg/ml of nicotine was used. We speculate that nicotine promoted the growth ofS. mutans, and moreS. mutanscells attracted moreC. albicanscells due to the interaction between two species. SinceS. mutansandC. albicansare putative pathogens for dental caries, the enhancement of the synergistic relationship by nicotine may contribute to caries development in smokers.