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Involvement of Streptococcus mutans in the pathogenesis of dental caries among human populations is well established. Here, we studied the effect of gallic acid, a naturally occurring polyphenol on certain cariogenic activities of S. mutans. Gallic acid inhibited the glycosyltransferase activity, a key enzyme of sucrose metabolism by 27-36% in S. mutans. Minimal inhibitory concentration (MIC) of gallic acid (136 µg/mL) inhibited the growth of S. mutans by 50%. About 0.4 mM of the polyphenol reduced biofilm formation by 40%, hydrophobicity 60% and acid production 36% by the organism under in vitro growth conditions. Fluorescence microscopy revealed that in absence of gallic acid, the cells were present as clumps, however in the presence of gallic acid (68 µg/mL), they were well segregated due to the inhibition of biofilm formation. The present findings suggest that gallic acid has cariostatic activity against S. mutans, which may have potential application in prevention of dental caries. [ABSTRACT FROM AUTHOR]

Sterols are essential components of the plasma membrane in eukaryotic cells. Nystatin-resistant erg mutants were used in the present study to investigate the in vitro effects of altered sterol structure on membrane lipid composition, fluidity, and asymmetry of phospholipids. Quantitative analyses of the wild type and mutants erg2, erg3 and erg6 revealed that mutants have lower sterol (free)-to-phospholipid molar ratios than the wild type. Phosphatidylcholine content was decreased in erg2 and erg3 mutants; however, it was increased in erg6 strains as compared to normals. Phosphatidylserine content was increased in the erg6 mutant only. Fluorescence anisotropy decreased with temperature in both probes, and was lower for mutants than for the wild type, suggesting an increased freedom in rotational movement due to decreased membrane order. Investigation of changes in the aminophospholipid transbilayer distribution using two chemical probes, trinitrobenzene sulfonic acid and fluorescamine, revealed that the amounts of phosphatidylethanolamine derivatized by these probes were quite similar in both the wild type and various erg strains. The present findings suggest that adaptive responses in yeast cells with altered sterol structure are possibly manifested through changes in membrane lipid composition and fluidity, and not through transbilayer rearrangement of aminophospholipids. [ABSTRACT FROM AUTHOR]

Introduction. Dextransucrase produced by Streptococcus mutans plays a vital role in the formation of dental caries by synthesizing exopolysaccharides from sucrose, which helps in the attachment of microbes to the tooth surface, causing caries. Exploring antibody production against S. mutans antigens could be an effective method to protect against dental caries. Hypothesis. Dextransucrase antibodies may help in the prevention of caries formation by inhibiting essential cariogenic factors. Aims. The aim of this study was to investigate the effects of dextransucrase antibodies on biofilm formation and certain associated cariogenic factors of S. mutans . Methodology. Dextransucrase was purified from culture of S. mutans . The antisera against the enzyme were raised in rabbits. The effect of dextransucrase antibodies on biofilm formation was studied using scanning electron microscopy, fluorescence microscopy and quantitative real-time polymerase chain reaction. The effects of the antibodies on associated cariogenic factors were examined using established methods. The cross-reactivity of antibodies with human lung, liver, heart, thyroid and kidney tissues was evaluated by immunohistochemistry. Results. Our findings showed impaired biofilm formation in S. mutans in the presence of dextransucrase antibodies. Genes associated with biofilm formation such as gtfB, gtfC, brpA, relA, Smu.630 and vicK were downregulated (50-97 %) by dextransucrase antibodies in S. mutans . The adherence of S. mutans to glass surface was reduced by 58 % and hydrophobicity was reduced by 55.2 % in the presence of the antibodies compared to the controls. Immunohistochemistry studies revealed no cross-reactivity of human tissues with dextransucrase antibodies. Conclusions. These findings suggest that antibodies raised against dextransucrase exhibit a profound inhibitory effect on biofilm formation and vital cariogenic factors of S. mutans , which supports the contention that dextransucrase could be a promising antigen to study for its anticariogenic potential.