In vitro activities of Acacia nilotica (L.) Delile bark fractions against Oral Bacteria, Glucosyltransferase and as antioxidant.

BACKGROUND: Dental caries and periodontal disease are the most common chronic infectious oral diseases in the world. Acacia nilotica was commonly known in Sudan as Garad or Sunt has a wide range of medicinal uses. In the present study, antibacterial activity of oral bacteria (Streptococcus sobrinus and Porphyromonas gingivalis), inhibitory activity against glucosyltransferase (GTF) enzyme and antioxidant activity were assayed for methanolic crude extract of A. nilotica bark and its fractions. METHODS: Methanoilc crude extract of A. nilotica bark was applied to a Sephadex LH-20 column and eluted with methanol, aqueous methanol, and finally aqueous acetone to obtain four fractions (Fr1- Fr4). Furthermore, the crude extract and fractions were subjected to analytical high performance liquid chromatography (HPLC). The crude extract and its fractions were assayed for antibacterial activity against S. sobrinus and P. gingivalis using a microplate dilution assay method to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), as well as GTF inhibition and antioxidant activity using ABTS radical scavenging method. RESULTS: Fractions (Fr1 and Fr2) exhibited MIC values of 0.3 mg/ml against the P. gingivalis. Additionally, Fr2 displayed MBC value of 1 mg/ml against two types of bacteria. Fr4 showed an especially potent GTF inhibitory activity with IC50 value of 3.9 µg/ml. Fr1 displayed the best antioxidant activity with IC50 value of 1.8 µg/ml. The main compound in Fr1 was identified as gallic acid, and Fr2 was mostly a mixture of gallic acid and methyl gallate. CONCLUSIONS: The results obtained in this study provide some scientific rationale and justify the use of this plant for the treatment of dental diseases in traditional medicine. A. nilotica bark, besides their antibacterial potentiality and GTF inhibitory activity, it may be used as adjuvant antioxidants in mouthwashes. Further studies in the future are required to identify the rest of the active compounds.

The role of the Acanthamoeba castellanii Sir2-like protein in the growth and encystation of Acanthamoeba.

BACKGROUND: The encystation of Acanthamoeba leads to the development of resilient cysts from vegetative trophozoites. This process is essential for the survival of parasites under unfavorable conditions. Previous studies have reported that, during the encystation of A. castellanii, the expression levels of encystation-related factors are upregulated. However, the regulatory mechanisms for their expression during the encystation process remains unknown. Proteins in the sirtuin family, which consists of nicotinamide adenine dinucleotide-dependent deacetylases, are known to play an important role in various cellular functions. In the present study, we identified the Acanthamoeba silent-information regulator 2-like protein (AcSir2) and examined its role in the growth and encystation of Acanthamoeba. METHODS: We obtained the full-length sequence for AcSir2 using reverse-transcription polymerase chain reaction. In Acanthamoeba transfectants that constitutively overexpress AcSir2 protein, SIRT deacetylase activity was measured, and the intracellular localization of AcSir2 and the effects on the growth and encystation of trophozoites were examined. In addition, the sirtuin inhibitor salermide was used to determine whether these effects were caused by AcSir2 overexpression RESULTS: AcSir2 was classified as a class-IV sirtuin. AcSir2 exhibited functional SIRT deacetylase activity, localized mainly in the nucleus, and its transcription was upregulated during encystation. In trophozoites, AcSir2 overexpression led to greater cell growth, and this growth was inhibited by treatment with salermide, a sirtuin inhibitor. When AcSir2 was overexpressed in the cysts, the encystation rate was significantly higher; this was also reversed with salermide treatment. In AcSir2-overexpressing encysting cells, the transcription of cellulose synthase was highly upregulated compared with that of control cells, and this upregulation was abolished with salermide treatment. Transmission electron microscope-based ultrastructural analysis of salermide-treated encysting cells showed that the structure of the exocyst wall and intercyst space was impaired and that the endocyst wall had not formed. CONCLUSIONS: These results indicate that AcSir2 is a SIRT deacetylase that plays an essential role as a regulator of a variety of cellular processes and that the regulation of AcSir2 expression is important for the growth and encystation of A. castellanii.

Vaticanol C, a phytoalexin, induces apoptosis of leukemia and cancer cells by modulating expression of multiple sphingolipid metabolic enzymes.

Resveratrol (RSV) has recently attracted keen interest because of its pleiotropic effects. It exerts a wide range of health-promoting effects. In addition to health-promoting effects, RSV possesses anti-carcinogenic activity. However, a non-physiological concentration is needed to achieve an anti-cancer effect, and its in vivo bioavailability is low. Therefore, the clinical application of phytochemicals requires alternative candidates that induce the desired effects at a lower concentration and with increased bioavailability. We previously reported a low IC50 of vaticanol C (VTC), an RSV tetramer, among 12 RSV derivatives (Ito T. et al, 2003). However, the precise mechanism involved remains to be determined. Here, we screened an in-house chemical library bearing RSV building blocks ranging from dimers to octamers for cytotoxic effects in several leukemia and cancer cell lines and their anti-cancer drug-resistant sublines. Among the compounds, VTC exhibited the highest cytotoxicity, which was partially inhibited by a caspase 3 inhibitor, Z-VAD-FMK. VTC decreased the expression of sphingosine kinase 1, sphingosine kinase 2 and glucosylceramide synthase by transcriptional or post-transcriptional mechanisms, and increased cellular ceramides/dihydroceramides and decreased sphingosine 1-phosphate (S1P). VTC-induced sphingolipid rheostat modulation (the ratio of ceramide/S1P) is thought to be involved in cellular apoptosis. Indeed, exogenous S1P addition modulated VTC cytotoxicity significantly. A combination of SPHK1, SPHK2, and GCS chemical inhibitors induced sphingolipid rheostat modulation, cell growth suppression, and cytotoxicity similar to that of VTC. These results suggest the involvement of sphingolipid metabolism in VTC-induced cytotoxicity, and indicate VTC is a promising prototype for translational research.

Enhanced secretion of cyclodextrin glucanotransferase (CGTase) by Lactococcus lactis using heterologous signal peptides and optimization of cultivation conditions.

In previous studies of Lactococcus lactis, the levels of proteins secreted using heterologous signal peptides were observed to be lower than those obtained using the signal peptide from Usp45, the major secreted lactococcal protein. In this study, G1 (the native signal peptide of CGTase) and the signal peptide M5 (mutant of the G1 signal peptide) were introduced into L. lactis to investigate the effect of signal peptides on lactococcal protein secretion to improve secretion efficiency. The effectiveness of these signal peptides were compared to the Usp45 signal peptide. The highest secretion levels were obtained using the G1 signal peptide. Sequence analysis of signal peptide amino acids revealed that a basic N-terminal signal peptide is not absolutely required for efficient protein export in L. lactis. Moreover, the introduction of a helix-breaking residue in the H-region of the M5 signal peptide caused a reduction in the signal peptide hydrophobicity and decreased protein secretion. In addition, the optimization of cultivation conditions for recombinant G1-CGTase production via response surface methodology (RSM) showed that CGTase activity increased approximately 2.92-fold from 5.01 to 16.89 U/ml compared to the unoptimized conditions.

Inhibition of streptococcal biofilm by hydrogen water.

OBJECTIVES: The accumulation of oral bacterial biofilm is the main etiological factor of oral diseases. Recently, electrolyzed hydrogen-rich water (H-water) has been shown to act as an effective antioxidant by reducing oxidative stress. In addition to this general health benefit, H-water has antibacterial activity for disease-associated oral bacteria. However, little is known about the effect of H-water on oral bacterial biofilm. The objective of this study was to confirm the effect of H-water on streptococcal biofilm formation. METHODS: In vitro streptococcal biofilm was quantified using crystal violet staining after culture on a polystyrene plate. The effect of H-water on the expression of genes involved in insoluble glucan synthesis and glucan binding, which are critical steps for oral biofilm formation, was evaluated in MS. In addition, we compared the number of salivary streptococci after oral rinse with H-water and that with control tap water. Salivary streptococci were quantified by counting viable colonies on Mitis Salivarius agar-bacitracin. RESULTS: Our data showed that H-water caused a significant decrease in in vitro streptococcal biofilm formation. The expression level of the mRNA of glucosyltransferases (gtfB, gtfc, and gtfI) and glucan-binding proteins (gbpC, dblB) were decreased remarkably in MS after H-water exposure for 60s. Furthermore, oral rinse with H-water for 1 week led to significantly fewer salivary streptococci than did that with control tap water. CONCLUSIONS: Our data suggest that oral rinse with H-water would be helpful in treating dental biofilm-dependent diseases with ease and efficiency.

Functional characterization and analysis of the Arabidopsis UGT71C5 promoter region.

In the present study, we isolated an Arabidopsis promoter, UGT71C5, and analyzed its role in the regulation of the light response mechanism. We constructed a fusion vector pBI121-pU-GUS by integrating the UGT71C5 promoter upstream of the GUS reporter gene in pBI121, and then transferred this vector into Arabidopsis plants. The GUS activity of the transgenic plants was detected using a spectrophotometer under normal growth conditions as well as under light, drought, and ABA stress-treatments. The obtained results indicated that the GUS activity of transgenic plants ranged in between the activities observed in wild-type and 35S transgenic plants, which were used as positive control. Light stress for 8 and 12 h increased the GUS activity in transgenic plants by 3 and 4 times, respectively, compared to the activity in these plants under normal conditions. No such change in the GUS activity was observed under drought and ABA-treated conditions. This suggests that the UGT71C5 promoter is light inducible. Our study provides helpful insights into the elucidation of inducible promoters in Arabidopsis and the molecular mechanisms of light response.

Effect of high-fructose corn syrup on Streptococcus mutans virulence gene expression and on tooth demineralization.

High-fructose corn syrup-55 (HFCS-55) has been widely welcomed in recent years as a substitute for sucrose on the basis of its favourable properties and price. The objective of this study was to determine the influence of HFCS-55 on the expression of Streptococcus mutans UA159 virulence genes and on tooth demineralization. Real-time reverse-transcription PCR (real-time RT-PCR) and microhardness evaluations were performed to examine gene expression and enamel demineralization, respectively, after treatment with HFCS-55 and/or sucrose. Significant up-regulation of glucosyltransferase B (gtfB) by HFCS-55 was found. A mixture of HFCS-55 and sucrose could positively enhance expression of glucan-binding protein (gbp) genes. Regarding acidogenicity, expression of the lactate dehydrogenase (ldh) gene was unaffected by HFCS-55. A notable finding in this study was that 5% HFCS-55 significantly enhanced expression of the intracellular response gene of the two-component VicRK signal transduction system (vicR). Demineralization testing showed that the microhardness of teeth decreased by a greater extent in response to HFCS-55 than in response to sucrose. The results indicate that HFCS-55 can enhance S. mutans biofilm formation indirectly in the presence of sucrose and that HFCS-55 has a more acidogenic potential than does sucrose. Summing up the real-time PCR and demineralization results, HFCS-55 appears to be no less cariogenic than sucrose in vitro - at least, not under the conditions of our experiments.

Relationship between fluoride concentration and activity against virulence factors and viability of a cariogenic biofilm: in vitro study.

Despite widespread use of various concentrations of fluoride for the prevention of dental caries, the relationship between fluoride concentration and activity against cariogenic biofilms has not been much studied. Herein we investigated the relationship between fluoride concentration and activity against virulence factors and viability of Streptococcus mutans biofilms. S. mutans biofilms were formed on saliva-coated hydroxyapatite discs. The 70-hour-old biofilms were exposed to 0, 1, 3, 10, 30, 100, 300, 1,000 or 2,000 ppm F(-). The changes of virulence factors and viability of the biofilms were analyzed using biochemical methods and laser scanning confocal fluorescence microscopy. At 1-2,000 ppm F(-), the activity of fluoride against acid production, acid tolerance, and extracellular polysaccharide formation of S. mutans biofilms accurately followed a sigmoidal pattern of concentration dependence (R(2) = 0.94-0.99), with EC50 values ranging from 3.07 to 24.7 ppm F(-). Generally, the activity of fluoride against the virulence factors was concentration-dependently augmented in 10-100 ppm F(-) and did not increase further at concentrations higher than 100 ppm F(-). However, fluoride did not alter glucosyltransferase activity and viability of S. mutans biofilm cells in all concentrations tested. These results can provide a basis for the selection of appropriate fluoride concentrations that reduce the physiological ability of cariogenic biofilms.

Scanning electron microscopic study of Piper betle L. leaves extract effect against Streptococcus mutans ATCC 25175.

INTRODUCTION: Previous studies have shown that Piper betle L. leaves extract inhibits the adherence of Streptococcus mutans to glass surface, suggesting its potential role in controlling dental plaque development. OBJECTIVES: In this study, the effect of the Piper betle L. extract towards S. mutans (with/without sucrose) using scanning electron microscopy (SEM) and on partially purified cell-associated glucosyltransferase activity were determined. MATERIAL AND METHODS: S. mutans were allowed to adhere to glass beads suspended in 6 different Brain Heart Infusion broths [without sucrose; with sucrose; without sucrose containing the extract (2 mg mL(-1) and 4 mg mL(-1)); with sucrose containing the extract (2 mg mL(-1) and 4 mg mL(-1))]. Positive control was 0.12% chlorhexidine. The glass beads were later processed for SEM viewing. Cell surface area and appearance and, cell population of S. mutans adhering to the glass beads were determined upon viewing using the SEM. The glucosyltransferase activity (with/without extract) was also determined. One- and two-way ANOVA were used accordingly. RESULTS: It was found that sucrose increased adherence and cell surface area of S. mutans (p<0.001). S. mutans adhering to 100 µm² glass surfaces (with/without sucrose) exhibited reduced cell surface area, fluffy extracellular appearance and cell population in the presence of the Piper betle L. leaves extract. It was also found that the extract inhibited glucosyltransferase activity and its inhibition at 2.5 mg mL(-1) corresponded to that of 0.12% chlorhexidine. At 4 mg mL(-1) of the extract, the glucosyltransferase activity was undetectable and despite that, bacterial cells still demonstrated adherence capacity. CONCLUSION: The SEM analysis confirmed the inhibitory effects of the Piper betle L. leaves extract towards cell adherence, cell growth and extracellular polysaccharide formation of S. mutans visually. In bacterial cell adherence, other factors besides glucosyltransferase are involved.

Scanning Electron Microscopic study of Piper betle L. leaves extract effect against Streptococcus mutans ATCC 25175

INTRODUCTION: Previous studies have shown that Piper betle L. leaves extract inhibits the adherence of Streptococcus mutans to glass surface, suggesting its potential role in controlling dental plaque development. OBJECTIVES: In this study, the effect of the Piper betle L. extract towards S. mutans (with/without sucrose) using scanning electron microscopy (SEM) and on partially purifed cell-associated glucosyltransferase activity were determined. MATERIAL AND METHODS: S. mutans were allowed to adhere to glass beads suspended in 6 different Brain Heart Infusion broths [without sucrose; with sucrose; without sucrose containing the extract (2 mg mL-1 and 4 mg mL-1); with sucrose containing the extract (2 mg mL-1 and 4 mg mL-1)]. Positive control was 0.12 percent chlorhexidine. The glass beads were later processed for SEM viewing. Cell surface area and appearance and, cell population of S. mutans adhering to the glass beads were determined upon viewing using the SEM. The glucosyltransferase activity (with/without extract) was also determined. One- and two-way ANOVA were used accordingly. RESULTS: It was found that sucrose increased adherence and cell surface area of S. mutans (p<0.001). S. mutans adhering to 100 µm² glass surfaces (with/without sucrose) exhibited reduced cell surface area, fuffy extracellular appearance and cell population in the presence of the Piper betle L. leaves extract. It was also found that the extract inhibited glucosyltransferase activity and its inhibition at 2.5 mg mL-1 corresponded to that of 0.12 percent chlorhexidine. At 4 mg mL-1 of the extract, the glucosyltransferase activity was undetectable and despite that, bacterial cells still demonstrated adherence capacity. CONCLUSION: The SEM analysis confrmed the inhibitory effects of the Piper betle L. leaves extract towards cell adherence, cell growth and extracellular polysaccharide formation of S. mutans visually. In bacterial cell adherence, other factors besides glucosyltransferase are involved.

Effect of garlic on bacterial biofilm formation on orthodontic wire.

OBJECTIVE: To examine the effect of garlic extract on the biofilm formation by Streptococcus mutans on orthodontic wire and on glucosyltransferase gene expression. MATERIALS AND METHODS: Growth inhibition of oral bacteria was tested after 50 µL of garlic extract was placed on an agar plate. The minimum inhibitory concentration (MIC) of garlic extract on S mutans growth was first determined. After cultivating streptococci in biofilm medium (BM)-sucrose with garlic extract and orthodontic wire, adenosine triphosphate (ATP) measurement and viable cell counting was performed from the bacteria attached on the wire. Scanning electron microscopy (SEM) analysis of morphology was observed on bacterial cells attached to orthodontic wire. The effect of garlic extract on gene expression was evaluated using quantitative real-time polymerase chain reaction (PCR) of glucosyltransferase. RESULTS: Though garlic extract had a clear antibacterial effect on all microorganisms, it also enhanced S mutans attachment on orthodontic wire. Low concentration of garlic extract also increased glucosyltransferase gene expression of S mutans. CONCLUSIONS: Despite its antibacterial function, garlic extract increases biofilm formation by S mutans to orthodontic wire, likely through upregulation of glucosyltransferase expression. Garlic extract may thus play an important role in increased bacterial attachment to orthodontic wires.

Anti-biofilm effect of dental adhesive with cationic monomer.

The incorporation of polymerizable cationic monomers has been attempted to generate dental resinous materials with antibacterial activity. This study tested the hypothesis that a dental adhesive containing a cationic monomer, methacryloxylethyl cetyl dimethyl ammonium chloride (DMAE-CB), would influence biofilm formation and gtf gene expression of Streptococcus mutans. The effect of the photo-polymerized DMAE-CB-incorporated adhesive on in vitro biofilm accumulation was investigated with spectrophotometry and scanning electron microscopy. The relative level of gtf gene expression by Streptococcus mutans in the biofilm was quantified by real-time reverse-transcription polymerase chain-reaction. The DMAE-CB-incorporated adhesive significantly decreased bio-film accumulation on its surface (P < 0.05), and suppressed the expression of gtfB and gtfC of Streptococcus mutans in the biofilm (P < 0.05). The results suggest that the cured DMAE-CB-incorporated adhesive may hamper biofilm accumulation via selective down-regulation of the expression of gtf genes in Streptococcus mutans.

Effect of antiplaque compounds and mouthrinses on the activity of glucosyltransferases from Streptococcus sobrinus and insoluble glucan production.

INTRODUCTION: The development of therapeutic agents inhibiting the activity of glucosyltransferases (GTF) and their production of glucans is a potential strategy to reduce dental decay. The aim of this study was first to characterize a GTF preparation from Streptococcus sobrinus ATCC 33478 and then to evaluate the effects of select compounds and mouthrinses on insoluble glucan (ISG) formation by combined GTFs. METHODS: The purity of the crude GTF mixture was assessed by electrophoresis. The effects of pH, temperature, sucrose, and dextran T10 concentrations on GTF activity were analyzed and the chemical structure of the products was investigated. Finally, the inhibition of GTF by commercial mouthrinses used in oral hygiene and their active components (chlorhexidine, polyphenolic compounds, fluoride derivatives, polyols, cetylpyridinium chloride, and povidone iodine) was analyzed through the reductions in the overall reaction rate and the quantity of ISG synthesized. RESULTS: The S. sobrinus ATCC 33478 crude GTF preparation obtained contains a mixture of four different GTFs known for this species. For optimal adherent ISG formation, the reaction parameters were 37 degrees C, pH 6.5, sucrose 50 g/l, and dextran T10 2 g/l. Under these conditions, the most effective agents were chlorhexidine, cetylpyridinium chloride, and tannic acid. Eludril, Elmex, and Betadine were the most effective inhibitors of all the mouthrinses tested. CONCLUSION: As the formulation of commercial products considerably influences the efficiency of active components, the fast representative ISG inhibition test developed in this study should be of great interest.

In vitro anti-bacterial and anti-adherence effects of natural polyphenolic compounds on oral bacteria.

AIMS: To investigate the action of different polyphenolic compounds, extracted from red wine, grape marc and pine bark, on oral bacteria. METHODS AND RESULTS: The anti-microbial activity of extracts was examined by determining the Minimal Inhibitory Concentration and Minimal Bactericidal Concentration using the macro dilution broth technique. Their effect on the adherence was tested on growing cells of Streptococcus mutans on a glass surface and on a multi-species biofilm grown on saliva-coated hydroxyapatite discs. The effect on glucosyltransferase activity was analysed through the reductions in the overall reaction rate and the quantity of insoluble glucan (ISG) synthesized. Pine bark and grape marc extracts were the most effective inhibitors of the multi-species biofilm formation and of the ISG synthesis. CONCLUSION: The tested components showed an interesting anti-plaque activity in vitro. SIGNIFICANCE AND IMPACT OF THE STUDY: This is, to our knowledge, the first and the most complete report on the properties of wine and pine bark extracts that could be used for oral disease prevention purpose.

Effects of Cistus-tea on bacterial colonization and enzyme activities of the in situ pellicle.

OBJECTIVES: Polyphenols are expected to have antibacterial properties. Cistus is a tea rich in polyphenols. The aim of the present in situ study was to investigate the effect of Cistus-tea on the pellicle and on the initial oral biofilm. METHODS: For in situ pellicle formation and initial biofilm formation, bovine enamel slabs were fixed on maxillary splints and carried by four subjects at buccal sites for up to 2 h. Bacteria present in 120-min pellicles were determined with DAPI-staining and fluorescence in situ hybridization with and without a 10 min rinse with Cistus-tea performed 1 min after incorporation of the slabs. In addition, amylase, lysozyme, glucosyltransferase and peroxidase activities immobilised in the pellicle layer were measured before and after rinsing for 10 min with Cistus-tea. RESULTS: The amount of bacteria detected in the 120-min biofilm was reduced significantly, if a 10 min rinse with Cistus-tea was performed one min after insertion of the enamel slabs. DAPI-staining yielded 13.2+/-3.5 for controls and 6.5+/-1.1 x 10(4) bacteria/cm(2), if a rinse with Cistus-tea was applied. Lysozyme, amylase and glucosyltransferase activities immobilised in the pellicle were not affected following a rinse with Cistus-tea. However, peroxidase activity was reduced significantly. CONCLUSIONS: Cistus-tea may be used to reduce the initial bacterial adhesion in the oral cavity.

Glucosylceramide synthase decrease in frontal cortex of Alzheimer brain correlates with abnormal increase in endogenous ceramides: consequences to morphology and viability on enzyme suppression in cultured primary neurons.

Abnormal increase in native long-chain ceramides (lcCer) in AD implicates roles in neuronal atrophy and cognitive dysfunction especially in view of divergent roles this second messenger plays in cell function. Since clearance is mediated by glucosylceramide synthase (GCS, EC 2.4.1.80) levels of the enzyme were compared for 18 samples of AD Brodmann area 9/10 frontal cortex with 11 age-matched controls. Western analysis for (ir)GCS showed a significant decrease in AD brain (p<0.01) consistent with the hypothesis that enzyme dysfunction contributes to neuronal decay. To examine kinetics and consequences to morphology, cerebellar granule cells were treated in vitro with d-threo-P4 (P4). This potent inhibitor of GCS induced a time- and concentration-dependent increase in lcCer parallel to loss of viability and dramatic changes in neuron/neurite morphology via caspase-independent pathways distinct from those of apoptosis or necrosis. Fluorescent labeling with NBD-sphingolipids or immunostaining with anti-synaptic or cytoskeletal markers showed unusual formation of globular swellings along neurites rich in synaptophysin that may resemble formation of dystrophic neurites in AD. Effects of the inhibitor were verified by changes in lcCer mass and turnover of (14)[C]-acetate and -galactose or NBD-labeled anabolic products. Addition of a panel of inhibitors of other pathways confirms GCS as the major route for clearance in the present model. Pretreatment with GM(1) whose turnover is compromised was protective and pointed to useful therapeutic applications by supplementing existing membrane stores prior to GSC dysfunction.

Anticariogenic properties of the extract of Cyperus rotundus.

Streptococcus mutans (S. mutans) is known as the causative bacteria in the formation of dental plaque and dental caries. The aim of this experiment was to investigate the effects of Cyperus rotundus (C. rotundus) tuber extract on the growth, acid production, adhesion, and water-insoluble glucan synthesis of S. mutans. The growth and acid production were reduced by the extract of C. rotundus in a dose dependent manner. The extract of C. rotundus markedly inhibited the adherence of S. mutans to saliva-coated hydroxyapatite beads (HAs). The adherence was repressed by more than 50% at the concentration of 0.5 mg/ml of the extract and complete inhibition was observed at the concentration of 4 mg/ml of the extract. On the activity of glucosyltransferase (GTFase) which synthesizes water-insoluble glucan from sucrose, the extract of C. rotundus showed more than 10% inhibition at a concentration of 2 mg/ml. These results suggest that C. rotundus may inhibit cariogenic properties of S. mutans. Further studies are necessary to clarify the active constituents of C. rotundus responsible for such biomolecular activities.

Effects of Nidus Vespae extract and chemical fractions on glucosyltransferases, adherence and biofilm formation of Streptococcus mutans.

Nidus Vespae (the honeycomb of Polistes olivaceous, P. japonicus Saussure and Parapolybiavaria fabricius) have been extensively used in traditional Chinese medicine, given their multiple pharmacological activities, including antimicrobial, anti-inflammatory, anti-virus, anti-tumor and anesthetic properties. The present study evaluated the anti-glucosyltransferases (GTFs) activity, anti-adherence and anti-biofilm properties of 95% ethanol/water extract, cyclohexane/ethyl acetate, petroleum ether/ethyl acetate and chloroform/methanol fractions of Nidus Vespae. Chloroform/methanol fraction showed a remarkable capacity for inhibiting the adherence of Streptococcus mutans ATCC 25175 to saliva-coated hydroxyapatite disc (S-HA) at sub-MC concentrations. In addition, the Nidus Vespae extract and chemical fractions significantly inhibited the activity of cell-associated and extracellular GTFs at sub-MIC concentrations, and the chloroform/methanol fraction was the most effective one. For the anti-biofilm activity assays, minimum biofilm inhibition concentrations (MBIC50) and minimum biofilm reduction concentrations (MBRC50) were determined using the microdilution method. The chloroform/methanol fraction showed the highest anti-biofilm activities with a MBIC50 of 8mg/ml and a MBRC(50) of 16mg/ml against Streptococcus mutans ATCC 25175. The significant inhibition of GTFs activity and biofilm formation demonstrated by Nidus Vespae shows it to be a promising natural product for the prevention of dental caries.

Molecular cloning, characterization and expression of a novel trehalose-6-phosphate synthase homologue from Ginkgo biloba.

In many organisms, trehalose acts as protective metabolite against harsh environmental stresses, such as freezing, drought, nutrient starvation, heat and salt. Herein a cDNA (designated as GbTPS, GenBank Accession Number AY884150) encoding a trehalose-6-phosphate synthase homologue was isolated and characterized from the living fossil plant, Ginkgo biloba, which is highly tolerant to drought and cold. GbTPS encoded an 868-amino-acid polypeptide with a predicted isoelectric point of 5.83 and molecular mass of 97.9 kD. Amino acid sequence alignment revealed that GbTPS shared high identity with class II trehalose-6-phosphate synthase homologues (67% identical to AtTPS7), but had only 17% and 23% of identity with OstA from Escherichia coli and ScTPS1 from S. cerevisiae, respectively. DNA gel blot analysis indicated that GbTPS belonged to a small multi-gene family. The expression analysis by RT-PCR showed that GbTPS expressed in a tissue-specific manner in G. biloba and might involve in leaf development. GbTPS was also found to be induced by a variety of stresses including cold, salt, drought and mannitol.

Sucrose synthase and RuBisCo expression is similarly regulated by the nitrogen source in the nitrogen-fixing cyanobacterium Anabaena sp.

In higher plants and cyanobacteria, sucrose (Suc) metabolism is carried out by a similar set of enzymes. The function and regulation of Suc metabolism in cyanobacteria has begun to be elucidated. In strains of Anabaena sp., filamentous nitrogen-fixing cyanobacteria, Suc synthase (SuS, EC 2.4.1.13) controls Suc cell level through the cleavage of the disaccharide. The present work shows that there are two sus genes in Anabaena (Nostoc) sp. that are co-regulated regarding the nitrogen source; however, only susA accounts for the extractable SuS activity and for the control of the Suc level. Primer extension analysis has uncovered the sequence of the Anabaena susA and susB ammonium-activated putative promoters, which share a high sequence similarity with that of rbcLS encoding ribulose bisphosphate carboxylase/oxygenase (EC 4.1.1.39) and other ammonium up-regulated genes. Moreover, susA and rbcLS expression is developmentally co-localized to the vegetative cells of the nitrogen-fixing cyanobacterial filaments. Our results strongly suggest the existence of a regulatory network that would coordinate the expression of key genes for Suc and nitrogen metabolism, carbon fixation, and development in Anabaena sp.