poster abstractStreptococcus mutans, a gram-positive facultatively anaerobic bacterium, is considered as
the primary contributor to caries due to its high acidogenicity and aciduricity. Smoking is
one of the risk factors of periodontal disease and dental caries. Nicotine is one of the
alkaloid pharmacologically active agents in tobacco. Previous studies indicated nicotine
stimulated S. mutans biofilm formation and metabolism. However, the detailed
mechanism is still unknown. Thus, the aim of this study is to investigate how nicotine
facilitates S. mutans biofilm formation focused on extracellular polysaccharide synthesis.
S. mutans UA159 (ATCC 700610) was used in the present study. Confocal laser scanning
microscopy (CLSM) was used to investigate the effect of 0, 1, 2 and 4 mg/ml nicotine on
24 h S. mutans biofilm extracellular polysaccharide (EPS) expression (red fluorescentlabeled)
and nucleic acid expression (green fluorescent-labeled). Western blot assays
were used to investigate the effect of 0, 1, 2 and 4 mg/ml nicotine on the expression of
glucosyltransferase (Gtfs), glucan-binding protein A (Gbp-A) and Gbp-B in 24 h S.
mutans biofilm cells. CLSM results indicated nicotine increased both EPS and nucleic
acid, and the ratio of EPS/nucleic acid was also increased. It implied EPS synthesis in
single S. mutans cells was stimulated by nicotine treatment. Biofilm thickness was thicker
in nicotine-treated groups than the non-treated group. Western blot assay results indicated
that nicotine stimulated GtfC, Gbp-A and Gbp-B expression, but decreased GtfB
expression. In conclusion, nicotine stimulates S. mutans cell proliferation and EPS
synthesis partially by increasing GtfC, Gbp-A and Gbp-B