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PubMed1995

Acid adaptation in Streptococcus mutans UA159 alleviates sensitization to environmental stress due to RecA deficiency.

A RecA-deficient stain of Streptococcus mutans, isolated previously, was found to be more susceptible than the prototroph organism to acid killing and also showed reduced colony-forming ability on sucrose-containing medium. The deficient strain was able to grow in chemostat culture at a low pH value of 5 and did not show reduced capacity to produce acid in standard pH-drop experiments with excess glucose. Moreover, it was able to undergo an adaptive response when grown at a low pH to become more resistant to acid killing and also to killing by ultraviolet radiation or hydrogen peroxide. In fact, after adaptation, it was nearly as resistant as the prototroph strain. These findings were interpreted, in part, in terms of an acid-inducible DNA repair system which functions independently of RecA.

Adaptation, Physiological↗

PubMed1981

Immunization with purified protein antigens from Streptococcus mutans against dental caries in rhesus monkeys.

Protein antigens I, I/II, II, and III were prepared from Streptococcus mutans (serotype c). Their immunogenicities and protective effects against dental caries were investigated in 40 rhesus monkeys kept entirely on a human-type diet, containing about 15% sucrose. Antigens I, I/II and, to a lesser extent, antigen II induced significant reductions in dental caries, as compared with sham-immunized monkeys. This was achieved with 1 or 2 doses of antigen, the first of which was administered with adjuvant (Freund incomplete adjuvant or aluminum hydroxide). There was no reduction in caries in monkeys immunized with antigen III. The reduction in caries in the animals immunized with antigens I or I/II was comparable to that in monkeys immunized with whole cells. Protection against caries was associated predominantly with serum and gingival crevicular fluid immunoglobulin G antibodies, which appeared to be directed against the antigen I determinant, but antibodies to antigen II, though not to antigen III, were also protective.

Animals↗

PubMed1982

Purification and properties of glucosyltransferase responsible for water-insoluble glucan synthesis from Streptococcus mutans.

A glucosyltransferase responsible for water-insoluble glucan synthesis was purified from the culture fluids of Streptococcus mutans 6715-15 strain by column chromatography on Toyopearl HW-60 and subsequently on hydroxyapatite. The enzyme preparation gave a single band on analysis by polyacrylamide gel electrophoresis. The pH dependency of the activity showed two optimal peaks at 5.8 and 7.3 and the Km values for sucrose were 1.4 and 3.3 mM at the respective optimal pHs. The molecular weight determined by sodium dodecyl sulfate gel electrophoresis was 180,000. Although the enzyme scarcely synthesized water-insoluble and water-soluble glucans from sucrose, water-insoluble glucan formed from sucrose in the presence of dextran T10 consisted of over 93% alpha-1, 3-glucosidic linkage. Analysis of the structure of water-insoluble glucan indicated that the enzyme catalyzed the formation of branch points in alpha-1,6-glucan (dextran) and transferred the glucosyl moiety of sucrose to the C-3 position of the branching glucose residue of dextran. Since this enzyme has not yet been registered, we named it mutansynthetase (EC 2.4.1.?).

Chemical Phenomena↗

PubMed2003

Comparison of different techniques of quantitative PCR for determination of Streptococcus mutans counts in saliva samples.

Saliva samples from 16 children with current caries activity were investigated for Streptococcus mutans using three different PCR techniques, and the results were compared with those of selective cultivation on mitis salivarius agar with bacitracin (MSB) (I, II: LightCycler - competitive PCR end-point analysis; III: LightCycler - kinetic real-time analysis; IV, V: block cycler - competitive PCR end-point analysis; VI: cultivation on MSB agar). In groups I, III, IV and VI the saliva samples were analyzed directly. A DNA preparation before PCR with added competitors was carried out in groups II and V to exclude the influence of PCR inhibitors. The coefficients of correlation ranged from 0.97 to 0.98 among the competitive PCR methods, 0.8 to 0.85 for competitive vs. real-time PCR and 0.5 to 0.65 for PCR vs. cultivation methods. Competitive PCR on the real-time instrument was found to be more rapid than, comparably sensitive to, but less reproducible than competitive PCR on a block cycler.

Bacteriological Techniques↗

PubMed1988

Physical and biochemical studies of Streptococcus mutans sediments suggest new factors linking the cariogenicity of plaque with its extracellular polysaccharide content.

Cultures of Streptococcus mutans MFe28 (serotype h) were grown with differing extracellular polysaccharide (EPS) content. Biochemical and physicochemical characteristics considered relevant to caries were measured. Acid production parameters measured in a pH-stat were: Vm = 0.76 +/- 0.14 mumol/g/sec (wet weight); apparent Km (acid production) = 100 mumol/L; molar yield = 1.97 +/- 0.25 mol acid/mol glucose. Acid anion inhibition of acid production was also noted. Buffering by the pure washed bacterial residue required approx. 112 mumol of base/g (wet weight) of residue to change the pH from 4 to 6.5, and this dropped almost to zero as the EPS content increased to 100%. Diffusion coefficients (D) in the residues were independent of EPS content over a wide range. When the effusion method was used, De (glucose) and De (acetate) were (3.26 +/- 0.6) and (5.05 +/- 0.8) x 10(-6) cm2/sec, respectively. The extracellular fluid fraction, measured by inulin exclusion, increased from 0.33 for the pure bacteria to 0.78 for the pure EPS. It is shown how, by these factors alone, and without any need for diffusion restriction, plaque EPS may lead to a lower pH at the tooth surface, thus increasing the cariogenic challenge.

Chemical Phenomena↗

PubMed1991

Activation of human monocytes by Streptococcus mutans serotype f polysaccharide: immunoglobulin G Fc receptor expression and tumor necrosis factor and interleukin-1 production.

Streptococcus mutans serotype f polysaccharide (poly f) was prepared from S. mutans whole cells by autoclaving. The poly f was purified by chromatography on DEAE Trisacryl M and Bio-Gel P100, treated with insoluble pronase, and resubjected to chromatography on DEAE Trisacryl M. Normal human blood monocytes, stimulated in vitro with purified poly f, produced extracellular tumor necrosis factor alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) in a dose-dependent fashion as determined by a heterologous two-site sandwich enzyme-linked immunosorbent assay. Poly f also increased the expression of monocyte cell surface receptors for the Fc part of human immunoglobulin G, activity which is correlated with an increase of the phagocytic activity of the stimulated monocytes. Polymyxin B had no effect on TNF-alpha and IL-1 beta release. Neutralization assays with anti-recombinant human TNF-alpha and anti-recombinant human IL-1 beta immunoglobulin G confirmed the fact that the cytotoxic and mitogenic mediators released by the poly f-stimulated monocytes were mainly TNF-alpha and IL-1 beta.

Antigens, Differentiation↗

PubMed1980

Evidence that Streptococcus mutans constructs its membrane with excess fluidity for survival at suboptimal temperatures.

When cells from cultures of Streptococcus mutans strain FA-1 grown at 37 degrees C were exposed to incubation temperatures of 26 degrees C or less for 5 min or more, an extensive aggregation of particles was observed on the convex fracture faces of their freeze-cleaved membranes. Aggregation of particles was accompanied by a parallel increase in the activation energy for growth. By shifting the growth temperature from 37 to 24 degrees C for one doubling of culture mass, the transition temperature for membrane particle aggregation could be lowered from about 26 to 0 degrees C. Although membrane lipids became enriched with unsaturated fatty acids during this period of growth at 24 degrees C, this enrichment was not accompanied by an increased growth rate of the culture. However, the period of growth at 24 degrees C did result in bacteria that could grow more rapidly at 10 degrees C than could bacteria directly transferred from cultures grown at 37 degrees C. These observations suggest that the increase in membrane fluidity that occurs when bacteria are grown at 24 degrees C doses not allow bacteria to grow faster at 24 degrees C, but rather allows them to adapt more readily to further decreases in growth temperature.

Cell Membrane↗

PubMed1986

Purification and characterisation of the extracellular D-glucosyltransferase from serotype c Streptococcus mutans.

A simple method of purification for the extracellular D-glucosyltransferase (GTase) from a serotype c strain Streptococcus mutans was developed using chromatography on DEAE-Sephacel and CM-cellulose. The GTase had a molecular weight of 155,000 and an isoelectric point of 7.4. The enzyme converted sucrose, in the absence of dextran T-10, into a branched (1----6)-linked alpha-D-glucan having some alpha-(1----3)-linked D-glucosyl residues. The GTase was similar to GTases which have been isolated from other strains of serotype c S. mutans and which synthesise water-soluble glucans. In addition, the amino acid composition of the GTase protein was relatively similar to those of the GTases from serotype g S. mutans which synthesise water-soluble and water-insoluble glucans.

Amino Acids↗

PubMed1982

Isolation and characterization of Streptococcus mutans mutants with altered cellular morphology or chain length.

A nitrosoguanidine-induced mutant, designated UAB90, of Streptococcus mutans PS14 (serotype c) strain UAB62, was identified on the basis of its unique colony morphology and isolated on brain heart infusion agar. Other mutants displaying similar colony morphologies on brain heart infusion agar were isolated after ethyl methane sulfonate mutagenesis of UAB62 and S. mutans 6715 (serotype g) strains UAB61 and UAB66, and these were found to exhibit abnormalities in cell morphology, chain length, or both. All mutants were examined further for (i) adherence and aggregation after overnight growth in medium containing sucrose, (ii) growth and aggregation in brain heart infusion broth and medium containing glucose, (iii) aggregation of nongrowing cells in the presence of 2 mg of sucrose per ml or 200 mug of dextran per ml, (iv) dextranase activity, and (v) ease of cell lysis. Mutants isolated included several with long chains of enlarged cocci, and two of these strains, UAB261 and UAB433, along with UAB90, were more susceptible to cell lysis than were their parents. UAB261, isolated from UAB62, maintained other parental characteristics, whereas UAB433, isolated from UAB66, lost its ability to aggregate in the presence of either sucrose or dextran. The "fragile" mutant UAB90 was particularly useful in the isolation of high-molecular-weight DNA for early gene cloning experiments by our laboratory. Two other cell morphology mutants, UAB272 from UAB66 and UAB289 from UAB61, did not lyse better than their parents, but both lacked measurable dextranase activity. A final mutant, UAB276 from UAB66, displayed only increased chain length without apparent cell morphology variations. Chains produced by this mutant were up to 10 times longer than those produced by UAB66. UAB276 lysed slightly less well than its parent but retained all other wild-type characteristics examined.

Adhesiveness↗

PubMed1980

Effect of dextran and ammonium sulphate on the reaction catalysed by a glucosyltransferase complex from Streptococcus mutans.

The highly aggregated proteins precipitated by (NH4)2SO4 from the culture fluid of three strains of Streptococcus mutans gradually released less aggregated glucosyltransferase activities - dextransucrase and mutansucrase - which catalysed the synthesis of water-soluble and insoluble glucans from sucrose. Mutansucrase was eluted from a column of Sepharose 6B before dextransucrase. This activity was lost during subsequent dialysis and gel filtration, but there was a corresponding increase in dextransucrase activity which catalysed the formation of soluble glucan when incubated with sucrose alone, and insoluble glucan when incubated with sucrose and 1.55 M-(NH4)2SO4. Relative rates of synthesis of soluble and insoluble glucan in the presence of 1.55 M-(MH4)2SO4 were dependent upon the enzyme concentration: high concentrations favoured insoluble glucan synthesis. Insoluble glucans synthesized by mutansucrase or by dextransucrase in the presence of 1.55 M-(NH4)2SO4 were more sensitive to hydrolysis by mutanase than by dextranse, but soluble glucans were more extensively hydrolysed by dextranase than by mutanase. Partially purified dextransucrase sedimented through glycerol density gradients as a single symmetrical peak with an apparent molecular weight in the range 100000 to 110000. In the presence of 1.55 M-(NH4)2SO4, part of the activity sedimented rapidly as a high molecular weight aggregate. The results strongly suggest that soluble and insoluble glucans are synthesized by interconvertible forms of the same glucosyltransferase. The aggregated form, mutansucrase, preferentially catalyses (1 leads to 3)-alpha bond formation but dissociates during gel filtration to the dextransucrase form which catalyses (1 leads to 6)-alpha bond formation.

Ammonium Sulfate↗

PubMed2003

Molecular analysis of the inhibitory effects of oolong tea polyphenols on glucan-binding domain of recombinant glucosyltransferases from Streptococcus mutans MT8148.

An oolong tea polyphenol (OTF6) has been shown to possess a strong anti-glucosyltransferase (GTF) activity and inhibit experimental dental caries in rats infected with mutans streptococci. The effects of OTF6 on the functional domains of GTFs of Streptococcus mutans, an N-terminal catalytic domain (CAT), and a C-terminal glucan-binding domain (GBD), were examined. The maximum velocity of glucan synthesis by recombinant GTFB (rGTFB) and GTFD (rGTFD) became significantly slower in the presence of OTF6, however, Km values remained stable when compared in their absence. These results suggest that OTF6 reduces glucan synthesis by non-competitively inhibiting the GBD of S. mutans GTFB and GTFD. Further, the recombinant proteins of CAT (rCAT) and GBD (rGBD) were expressed using Escherichia coli, and purified by affinity column chromatography. rGBD but not rCAT was found to possess dextran-binding activity, which was shown to be inhibited by OTF6. These results indicate that OTF6, a polymeric polyphenol specific for oolong tea is able to reduce glucan synthesis by inhibiting the GBD of S. mutans GTFB.

Binding Sites↗

PubMed2001

Effect of water storage of E-glass fiber-reinforced composite on adhesion of Streptococcus mutans.

This study investigated the effect of water storage of fiber-reinforced composite on the adhesion of Streptococcus mutans (S. mutans) and its ability to stay adhered and multiply on the FRC. The materials (E-glass fibers and denture base polymer) were stored in water for 14 or 30 days or left dry. Water contact angles of the materials before and after water storage were determined. Test specimens, with or without parotid saliva or serum pellicle, were incubated in a suspension of S. mutans allowing initial adhesion to occur. Bacterial adhesion and multiplication was studied using scanning electron microscopy. Contact angles of both materials were significantly reduced after water storage indicating an increase in surface free energy. When studied without a surface pellicle, water storage significantly increased adhesion of S. mutans to both glass and polymer. Saliva coating of the materials resulted in higher degree of adhesion to glass fibers in comparison with polymer and after 14 days water storage glass bound over twice as much S. mutans cells than the polymer matrix. Bacterial growth and biofilm formation occurred equally on both materials. The results of this in vitro study suggest that in order to avoid the possible increase in S. mutans adhesion, the reinforcing glass fibers should be covered with the matrix polymer of the composite.

Bacterial Adhesion↗

PubMed1978

Production of extracellular and cell-associated glucosyltransferase activity by Streptococcus mutans during growth on various carbon sources.

The production of extracellular and cell-associated glucosyltransferase activity by Streptococcus mutans strain GS-5 was examined during growth on various carbon sources in a chemically defined medium. S. mutans cells produced glucosyltransferase activity only during logarithmic growth when glucose, fructose, mannitol, or sorbitol was the sole carbon source. Cells growing on mannitol or sorbitol produced approximately half as much extracellular glucosyltransferase activity as cells growing on glucose, although the proportions of the glucosyltransferase activity capable of synthesizing insoluble glucans were similar. Cells growing on fructose produced slightly more extracellular glucosyltransferase activity than cells grown on glucose, yet the proportion of the glucosyltransferase activity capable of synthesizing insoluble glucans was again similar to glucose cultures. S. mutans cells growing in the presence of both glucose and mannitol displayed diauxic growth and initial preferential utilization of glucose. Glucosyltransferase enzyme production occurred only during the phases of cell growth in the presence of the two carbon sources. The cell-associated glucosyltransferase activities of glucose-, fructose-, mannitol-, and sorbitol-grown cells were relatively low, yet all the cells were capable of adherence to glass in the presence of sucrose. When glucose-containing cultures of S. mutans were supplemented with sucrose, extracellular glucosyltransferase activity first became cell associated and then appeared to become inactivated, presumably due to the accumulation of insoluble glucans.

Carbohydrate Metabolism↗

PubMed1978

Ability of Streptococcus mutans and a glucosyltransferase-defective mutant to colonize rodents and attach to hydroxyapatite surfaces.

A mutant of Streptococcus mutans forming little or no cell-associated glucosyltransferase attached to the teeth of rats and to saliva-treated hydroxyapatite comparably to its parent.

Animals↗

PubMed1992

Characterization of the Streptococcus mutans GS-5 fruA gene encoding exo-beta-D-fructosidase.

The complete nucleotide sequence (5,010 bp) of the fructanase gene (fruA) and flanking regions of the chromosome of Streptococcus mutans GS-5 was determined. The fruA gene appears to be the sole transcript arising from a proximal promoter. The presumed precursor of the secreted FruA protein consists of 1,423 amino acids, and it has an M(r) of 158,656 and a pI of 4.82. The N terminus of FruA has characteristics in common with signal peptides of gram-positive organisms. The C terminus consists of a serine- and threonine-rich region, followed by the peptide LPDTGD, 4 charged amino acids, 21 amino acids with a strongly hydrophobic character, and a charged pentapeptide tail, which are proposed to correspond to the wall-spanning region, the LPXTGX consensus sequence, and the membrane-spanning domains of surface-associated proteins of gram-positive cocci. The FruA protein has significant homology with the Bacillus subtilis levanase (SacC), the Bacteroides fragilis levanase (ScrL), yeast invertases, and a number of other beta-fructosidases but not with fructosyltransferase, glucosyltransferases, or glucan-binding proteins of oral streptococci. Genes with homology to fruA were detected in S. mutans serotype c, e, and f strains, Streptococcus rattus, Streptococcus salivarius, and Streptococcus sanguis. A deletion derivative of FruA lacking the C-terminal 437 amino acids was still functional and could hydrolyze beta-(2,6)- and beta-(2,1)-linked sugars, but with altered preference for substrates. The data begin to define functional domains of the FruA protein and potential regulatory sites for induction, repression, growth rate control, and posttranslational localization of this multifunctional enzyme.

Amino Acid Sequence↗

PubMed1995

Mechanism of inhibition of glycolysis in Streptococcus mutans NCIB 11723 by chlorhexidine.

Inhibition of the rate of acid production from glucose by the cells of Streptococcus mutans NCIB 11723 was directly related to the concentrations of 0.075 to 0.20 mM chlorhexidine. Lactate production was inhibited to a greater extent than acetate and formate. Quantification of glycolytic intermediates revealed that the steps in glycolysis inhibited by chlorhexidine were the reactions catalyzed by phosphofructokinase and glyceraldehyde 3-phosphate dehydrogenase and/or phosphoglycerate kinase. However, the activities of these enzymes were not decreased in cells treated with the inhibitor. It was demonstrated that chlorhexidine caused leakage of metabolites from the cells. Our results indicate that the decreased rate of glycolysis caused by chlorhexidine is due to the leakage of metabolic intermediates and not to direct effects on enzymes involved in glycolysis by S. mutans NCIB 11723.

Acetates↗

PubMed1984

Lack of cross-reactivity of antibodies to ribosomal preparations from Streptococcus mutans with human heart and kidney antigens.

Previous studies have suggested that sera from animals immunized with whole Streptococcus mutans cells may cross-react with human and monkey heart sarcolemmal tissues. In the present study, sera and saliva from rats and rabbits immunized peripherally with ribosomal preparations from S. mutans 6715 (serotype g) or GS-5 (serotype c) were examined for their ability to react with normal human heart sarcolemmal and kidney glomerular tissues by using enzyme-linked immunosorbent and immunofluorescence assays. The results showed that antibodies to serotype g and c ribosomal preparations do not react with either the human heart or renal antigens. Sera from mice immunized with human heart tissue and from a patient with a high anti-streptolysin O titer reacted strongly with human heart sarcolemmal and kidney glomerular tissues. These data indicated that ribosomal preparations from S. mutans lack the putative human heart cross-reactive determinant and suggest that the use of an S. mutans ribosomal vaccine against dental caries may not be pathogenic to human heart or renal tissues.

Animals↗

PubMed1990

Immunological cross-reactivity between Streptococcus mutans and human heart tissue examined by cross-immunization experiments.

Hyperimmunization of rabbits with Streptococcus mutans or other related cariogenic streptococci sometimes induces serum antibodies that react with human heart muscle. To determine whether antigen I/II (AgI/II), a major surface protein antigen present in most human isolates of these organisms, was responsible for inducing cross-reactive antibodies, we tested it for antigenic similarity to heart components, exploiting the ability of immune systems to mount anamnestic responses to antigens previously encountered. Mice immunized with a strain of Streptococcus pyogenes type M6, known to be heart cross-reactive, or with intact S. mutans cells developed antibodies that could be detected on a human heart sarcolemmal preparation. However, mice immunized with AgI/II and boosted with sarcolemma were unable to develop significant antisarcolemmal antibodies attributable to prior sensitization by AgI/II. Similarly, AgI/II was unable to recall antisarcolemmal responses in mice previously immunized with sarcolemma. Nevertheless, strong immunoglobulin G antibody responses to AgI/II were detected at the single-cell level in spleens and as circulating antibodies in all mice immunized with AgI/II or AgI/II-bearing S. mutans. We conclude that the ability of S. mutans to induce heart-reactive antibodies is not due to antigenic similarity between AgI/II and components of human heart but may be caused by other cross-reactive antigens in the bacterial cells or by nonspecific stimulation of the immune system.

Animals↗