Browsing by Subject "NICOTINE"

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    EFFECT OF NICOTINE ON METABOLISM OF STARVED AND UNSTARVED STREPTOCOCCUS MUTANS
    (Office of the Vice Chancellor for Research, 2011-04-08) RODENBECK, JESSICA; GREGORY, RICHARD L.
    Streptococcus mutans is the major etiological agent of dental caries. Nicotine is the addictive ingredient present in most tobacco products that has been shown to have an effect on the growth and metabolism of oral bacteria, specifically S. mutans. This same bacterium has been recently linked to heart disease. Smokers regularly introduce this chemical into their system which causes an increased growth and metabolic rate of the bacteria, thus increasing their chances for dental caries. This research worked to further qualify the increase of metabolic rates by subjecting the bacteria to nicotine in a starved environment, on the basis that humans do not constantly have nutrients available to oral bacteria. Metabolic rates of an established biofilm of S. mutans were measured through an XTT and menadione assay with a spectrophotometer. The unstarved bacteria were grown in a full concentration of TSBS while the starved were grown in a 1:10 dilution of TSBS with sterile saline in various nicotine concentrations (0.0, 0.25, 0.50, 1.0, 2.0, 4.0, 8.0, 16.0, 32.0, 64.0, and 128.0 mg/ml). As the concentration of nicotine increase, the metabolic rates of S. mutans also increased. The high concentrations in which the bacteria were no longer metabolically active are very high and a normal smoker would not be able to reach these concentrations. However, as more nicotine is present in smokers these more metabolically active bacteria would be more likely to cause caries.
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    EFFECTS OF NICOTINE ON QUORUM SENSING IN STREPTOCOCCUS MUTANS
    (Office of the Vice Chancellor for Research, 2012-04-13) Bikormana, Emmanuel; Huang, Ruijie; Li, Mingyun; Gregory, Richard L.
    Streptococcus mutans is gram-positive cocci, facultative anaerobic bacterium commonly found in the human oral cavity, and significantly contributes to caries. The quorum sensing system plays an important role in microbial cell-cell interactions that leads to development of dental plaque. S. mutans produces glucosyltransferases together with the glucan binding proteins in order to facilitate the adherence of glucans to the tooth surface, thereby forming biofilms. Moreover, previous studies indicate that in the presence or absence of sucrose, a cell surface protein called antigen I/II plays an important role in the adherence process of S. mutans. There is a relationship between smoking and dental caries, in which the smoking population has a higher incidence of dental caries than a non-smoking population. Nicotine is one of the most important components in tobacco. In this study we investigated the effects of nicotine on quorum sensing in S. mutans. An S. mutans wild type UA159 and its knockout mutants defective in comC, comD and comE were used to investigate planktonic cell growth, the biofilm formation and biofilm metabolism at different concentrations of nicotine (0-32 mg/ml). The effects of nicotine on quorum sensing for S. mutans’ biofilm formation was evaluated using sucrose-dependent and sucrose-independent assays. The results indicate that S. mutans UA159 and its knockout mutants had no substantial differences in planktonic cell growth. In the presence of sucrose, the comC mutant was unable to produce biofilms, whereas the biofilm formation and biofilm metabolism of the comD and comE mutants were enhanced with increased nicotine concentration as with UA159 up to 8 mg/mL of nicotine. However, in the absence of sucrose, it was observed that the ComC mutant formed biofilms relatively similar to UA159. Biofilm formation in the comD and comE mutants was also enhanced with the increase of nicotine concentration up to 4 and 2 mg/mL, respectively. The results suggest that nicotine enhances the adherence process in S. mutans by antigen I/II through the comDE signaling pathway. However, the fact that the comC mutant produced biofilm in the absence of sucrose, but not in the presence of sucrose, indicates that the activity of antigen I/II is activated through different cell-cell signaling pathways depending on the amount of sucrose present.