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PubMed1990

Preliminary characterization of four bacteriocins from Streptococcus mutans.

The various properties of the inhibitory substances produced by Streptococcus mutans strains C67-1, Ny257-S, Ny266, and T8, and the fact that inhibitory zones produced could not be associated with lactic acid (or other organic acids), bacteriophages, or hydrogen peroxide indicate that these substances can be classified as mutacins. The substances produced by strains C67-1, Ny266, and T8 possessed similar properties. They were shown to be thermoresistant (100 degrees C, 30 min), low molecular weight (less than 3500) substances sensitive to proteolytic enzymes (chymotrypsin, papain, pronase E, proteinase K, and trypsin) and they were active against most of the Gram-positive bacteria tested but not against most of the Gram-negative bacteria. The substance produced by strain Ny257-S differs from the other three by its narrower activity spectrum, its lower thermoresistance (80 degrees C, 30 min), and its higher molecular weight (8,000-14,000). The gene or the genes coding for the mutacins are probably located on the chromosome since no plasmid DNA could be detected in these four producing strains. Restriction-fragment patterns of C67-1 and T8 suggest that these strains are closely related, as supported by the strong similarity observed between the properties of their mutacins.

Bacteriocins↗

PubMed1989

Sequence analysis of the wall-associated protein precursor of Streptococcus mutans antigen A.

The nucleotide sequence has been determined for the Streptococcus mutans wall-associated protein A (wapA) gene from serotype c strains Ingbritt and GS5. The nucleotide sequence for each wapA gene was virtually identical, although the gene from strain GS5 contained a 24 base pair deletion. A 29 amino acid signal peptide was specified by each wapA gene with a mature protein of 424 amino acids (Mr, 45,276) for strain Ingbritt and 416 amino acids (Mr, 44,846) for strain GS5. In the C-terminal region of the wall-associated protein A, considerable sequence similarity was found with the membrane anchor region of proteins from other Gram-positive organisms such as the group A streptococcal M protein and the group G streptococcal IgG binding protein. Adjacent to the proposed membrane anchor is a highly hydrophilic region which may span the cell wall; both sequence data and experimental evidence indicate the existence of a region immediately outside the wall at which proteolytic cleavage occurs to release antigen A of Mr 29,000 into the culture supernatant. Thus, the wall-associated protein A is a precursor of the 29,000 Mr antigen A.

Amino Acid Sequence↗

PubMed1981

Lysis of Streptococcus mutans by hen egg white lysozyme and inorganic sodium salts.

Streptococcus mutans BHT was grown in a synthetic medium containing radioactive thymidine to monitor deoxyribonucleic acid release. Kinetic experiments demonstrated that although lysozyme alone could not liberate deoxyribonucleic acid, cellular deoxyribonucleic acid was liberated from lysozyme-treated cells by addition of low concentrations of inorganic sodium salts. When the salts were tested for their ability to dislodge cell-bound tritiated lysozyme, the extent of the initial release of enzyme by individual anions correlated with the anion potency for deoxyribonucleic acid liberation (SCN- greater than ClO4- greater than I- greater than Br- greater than NO3- greater than Cl- greater than F-), although the total amount of lysozyme dislodged did not correspond directly with cell lysis. Differences in the effectiveness of anions (SCN-, HCO3-, Cl- and F-) in potentiating cell lysis could be enhanced or minimized by varying the lysozyme, anion, and bacterial cell concentrations. As the anion concentration was increased for each enzyme concentration and cell concentration, the lysis increased, in some cases markedly, until maximum levels of released deoxyribonucleic acid were attained. The maximum levels of lysis of SCN- and HCO3- were similar and were greater than those for Cl- and F-. In addition, the maximum levels were observed to increase for each of the anions as the concentration of lysozyme increased.

Anions↗

PubMed2005

Stimulation of various functions in murine peritoneal macrophages by glucans produced by glucosyltransferases from Streptococcus mutans.

The glucan that was produced by glucosyltransferases (GTFs) from Streptococcus mutans was examined for its stimulating functions toward murine peritoneal macrophages. Soluble glucan was obtained by the reaction with cell-free crude GTFs and sucrose, followed by ethanol precipitation, dispersion in water and re-precipitation by ethanol. Soluble glucan, those average molecular weight was about 3 x 10(5), was composed of mixture of alpha-1,6 and alpha-1,3 linkages in a 3:1 ratio. When 30 and 60 microg/ml of the glucan was incubated with peritoneal macrophages, the lysosomal phosphatase activity was increased in a dose-dependent manner, indicating that soluble glucan may activate macrophages. To examine its effects on the various functions of macrophages, soluble glucan was orally administered daily at a level of 100 mg/kg of body weight to C57BL/6 mice. Significant stimulation of the production of H2O2 by the macrophages was observed without any increase in NO production. The production of tumor necrosis factor-alpha (TNF-alpha) by the macrophages was also stimulated from 538.73-555.06 pg/ml to 585.73-596.40 pg/ml during 15 days of oral administration of soluble glucan. The cytotoxicity of peritoneal macrophages against B16 tumor cells was significantly enhanced by 25-38% during 15 days of oral administration. These results may indicate that soluble glucan stimulates the immune functions of macrophages.

Animals↗

PubMed2001

Crystal structure of Streptococcus mutans pyrophosphatase: a new fold for an old mechanism.

BACKGROUND: Streptococcus mutans pyrophosphatase (Sm-PPase) is a member of a relatively uncommon but widely dispersed sequence family (family II) of inorganic pyrophosphatases. A structure will answer two main questions: is it structurally similar to the family I PPases, and is the mechanism similar? RESULTS: The first family II PPase structure, that of homodimeric Sm-PPase complexed with metal and sulfate ions, has been solved by X-ray crystallography at 2.2 A resolution. The tertiary fold of Sm-PPase consists of a 189 residue alpha/beta N-terminal domain and a 114 residue mixed beta sheet C-terminal domain and bears no resemblance to family I PPase, even though the arrangement of active site ligands and the residues that bind them shows significant similarity. The preference for Mn2+ over Mg2+ in family II PPases is explained by the histidine ligands and bidentate carboxylate coordination. The active site is located at the domain interface. The C-terminal domain is hinged to the N-terminal domain and exists in both closed and open conformations. CONCLUSIONS: The active site similiarities, including a water coordinated to two metal ions, suggest that the family II PPase mechanism is "analogous" (not "homologous") to that of family I PPases. This is a remarkable example of convergent evolution. The large change in C-terminal conformation suggests that domain closure might be the mechanism by which Sm-PPase achieves specificity for pyrophosphate over other polyphosphates.

Binding Sites↗

PubMed1985

Kinetic studies on dextransucrase from the cariogenic oral bacterium Streptococcus mutans.

The kinetic mechanism of dextransucrase was studied using the Streptococcus mutans enzyme purified by affinity chromatography to a specific activity of 36.9 mumol/min/mg of enzyme. In addition to dextran synthesis, the enzyme catalyzed sucrose hydrolysis and isotope exchange between fructose and sucrose. The rates of sucrose hydrolysis and dextran synthesis were partitioned as a function of dextran concentration such that exclusive sucrose hydrolysis was observed in the absence of dextran and exclusive dextran synthesis at high dextran concentrations. An analogous situation was observed with fructose-dependent partitioning of sucrose hydrolysis and fructose exchange. Steady state dextran synthesis and fructose isotope exchange kinetics were simplified by assay at dextran or fructose concentrations high enough to eliminate significant contributions from sucrose hydrolysis. This limited dextran synthesis assays to dextran concentrations above apparent saturation. The limitation was diminished by establishing conditions in which the enzyme does not distinguish between dextran as a substrate and product which allowed initial discrimination among mechanisms on the basis of the presence or absence of dextran substrate inhibition. No inhibition was observed, which excluded ping-pong and all but three common sequential mechanisms. Patterns of initial velocity fructose production inhibition and fructose isotope exchange at equilibrium were consistent with dextran synthesis proceeding by a rapid equilibrium random mechanism. A nonsequential segment was apparent in the exchange reaction between fructose and sucrose assayed in the absence of dextran. However, the absence of detectable glucosyl exchange between dextrans and the lack of steady state dextran substrate inhibition indicate that glucosyl transfer to dextran must occur almost exclusively through the sequential route. A review of the kinetic constants from steady state dextran synthesis, fructose product inhibition, and fructose isotope exchange showed a consistency in constants derived from each reaction and revealed that dextran binding increases the affinity of sucrose and fructose for dextransucrase.

Chromatography, Affinity↗

PubMed1982

Evidence for the involvement of proton motive force in the transport of glucose by a mutant of Streptococcus mutans strain DR0001 defective in glucose-phosphoenolpyruvate phosphotransferase activity.

Streptococcus mutans DR0001 and a glucose-phosphotransferase (PTS)-defective mutant, DR0001/6, were grown anaerobically in a chemostat with a glucose limitation at dilution rates (D) of 0.04 to 0.6 h(-1) (mean generation time, 17 to 1.2 h). The mutant possessed only 15% of glucose-PTS activity of the wild type and gave cell yields (19%) less than those of the wild type. Glucose-PTS activity in strains DR0001 was maximum at D = 0.1 h(-1) and was adequate to account for transport in the chemostat at all dilution rates except D = 0.6 h(-1), at which it was 80% of the actual glucose uptake activity. The mutant DR0001/6, on the other hand, possessed only sufficient glucose-PTS activity to sustain growth at below D = 0.1 h(-1), indicating the presence of an alternate transport activity. This was confirmed in glycolytic rate experiments with washed cells, which demonstrated that the mutant showed rates 11- to 27-fold higher than that accountable via glucose-PTS activity alone. The wild-type organism contained both a high (K(s), 6.7 to 8.0 muM)- and a low (K(s), 57 to 125 muM)-affinity transport system, whereas the glucose-PTS-defective mutant contained only the low-affinity system (K(s), 62 to 133 muM). The glucose-PTS was shown to be the high-affinity system. Glucose uptake by the mutant was unaffected by 8 mM sodium arsenate, 10 mM azide, and 10 mM dinitrophenol but was completely inhibited by 0.05 mM sodium iodoacetate. Glycolysis in the organism was almost completely inhibited by 0.25 mM N',N' -dicyclohexylcarbodiimide (DCCD), indicating the involvement of an ATPase in glucose uptake. The ionophores carbonylcyanide-m-chlorophenylhydrazone and tetrachlorosali-cylanilide were inhibitory at concentrations of 10 muM, suggesting that a proton gradient was important in the transport process. Higher levels of DCCD and the ionophores were required to inhibit the wild-type organism to the same degree. A mechanism is proposed for the alternative transport system whereby proton motive force is created by the extrusion of protons by the DCCD-sensitive ATPase and glucose is transported down a proton gradient in a symport with protons.

Adenosine Triphosphatases↗

PubMed1983

Protoplast and cytoplasmic membrane preparations from Streptococcus sanguis and Streptococcus mutans.

Protoplasts were prepared from Streptococcus sanguis and some S. mutans serotypes by use of lysozyme (EC 3.2.1.17) under particular conditions: cells had to be grown in DL-threonine (20 mM) and harvested in early exponential phase. The efficiency of protoplast formation was enhanced by two additional steps: plasmolysis (in 12% PEG), prior to addition of lysozyme, and a swirling phase, after the enzymic action. This procedure allowed us to obtain clean protoplasts, with only 0.5% contamination by bacterial cell walls. Up to 90% protoplast lysis was obtained in 0.5 M-NaCl. Cytoplasmic membrane purification was achieved by centrifugation on a glycerol cushion.

Bacteriological Techniques↗

PubMed1989

[Proliferation and superoxide dismutase (SOD) induction of Streptococcus mutans (sobrinus) B13. 1. Metal requirement].

Many of micro-organisms under aerobic conditions showed oxygen tolerance caused by the induction of several oxygen-derived free radical scavengers. In the present study, we tried to clarify the changes of active oxygen metabolism of streptococcus mutans (sobrinus) B13 under aerobic conditions. Aerobic and anaerobic culture of streptococcus mutans (sobrinus) B13 was made in normal, metal chleted, and metal supplemented medium. Superoxide dismutase (SOD) activity and bacterial proliferation were determined on the cultured cells. We obtained the following results. 1) In the anaerobic normal medium, SOD activity was not detected, but proliferation was observed. On the other hand, the neither were detected in the metal chleted medium. 2) No effect was observed on the induction of SOD activity and proliferation by the supplementation of copper in the metal chelated medium. 3) We observed positive effects on the induction of SOD activity and proliferation by the supplementation of iron, managnese, or both in the metal chlated medium under aerobic condition. Based on the above results, we found that iron and manganese were essential metals for SOD activity induction. Moreover, we suggested that there was close association of the aerobic bacterial proliferation with the induction of oxygen-derived free radical scavengers.

Energy Metabolism↗

PubMed1981

Thiocyanate as a cofactor in myeloperoxidase activity against Streptococcus mutans.

Inhibition of glycolysis of some oral bacteria was established in vitro by an antibacterial system, consisting of myeloperoxidase, H2O2, and a cofactor. When thiocyanate was used in physiological concentration as a cofactor, the system acted (at low pH) bactericidally on Streptococcus mutans, as indicated by the determination of viable counts. However, at neutral pH, the glycolysis of Streptococcus mutans was inhibited, while its viability remained unaffected. The possible role of such a pH-dependent antibacterial system in the oral cavity is discussed.

Androstenedione↗

PubMed2004

Hydroquinone, a control agent of agglutination and adherence of Streptococcus mutans induced by sucrose.

Hydroquinone was found to alter agglutination of Streptococcus mutans induced by sucrose. The newly formed agglutination product produced by hydroquinone does not kill this cariogenic bacterium and the formation is reversible. The agglutination altering activity of hydroquinone seems to be specific for strains of S. mutans. As a result, hydroquinone inhibits sucrose-induced adherence of S. mutans.

Anti-Bacterial Agents↗

PubMed1979

Stability of the resident microflora and the bacteriocinogeny of Streptococcus mutans as factors affecting its establishment in specific pathogen-free rats.

The outcome of the experimental implantation of Streptococcus mutans strains in humans and animals is unpredictable, and neither success nor failure can be explained. It seems logical to assume that, apart from dietary and host factors, the characteristics of the S. mutans strain involved and those of the resident plaque microflora are important in colonization. For example, previous work in this laboratory suggested that bacteriocin production accounts at least in part for the establishment of an invading bacterium in a microbial ecosystem. In the present study, a complex specific pathogen-free Ny plaque ecosystem was obtained by the inoculation of specific pathogen-free rats with Actinomyces viscosus Ny1 and S. sanguis Ny101, and the establishment of S. mutans in such rats was then examined. It was found that bacteriocinogenic (bac(+)) strains generally colonized in much higher proportions than non-bacteriocinogenic (bac(-)) strains. Moreover, the longer the delay in introducing S. mutans, the poorer was its establishment. Shortly after inoculation of strains Ny1 and Ny101, there is probably a transient state in which microbial equilibrium has not been reached, but later the specific pathogen-free Ny system attains a stable climax community which more strongly resists invaders. The ability of a number of S. mutans strains to establish in such a climax community was then examined, and it was found that bac(+) strains generally established at a higher level than did bac(-) strains. In summary, it was concluded that, although the bac(+) state is an important property in the successful invasion of a plaque by S. mutans, the stability of the resident microflora is also an important factor.

Actinomyces↗

PubMed2006

[Construction of Streptococcus mutans luxS gene allelic exchange plasmid].

OBJECTIVE: It is reported that Streptococcus mutans luxS gene may have an important role in the interspecies quorum sensing system. To construct the S. mutans luxS gene knockout mutant, this research aim to construct the luxS gene allelic exchange plasmid. METHODS: The upstream and downstream flank DNA fragments of S. mutans luxS gene (Xup, Xdn)and the E. coli kanamycin resistance gene (Kana) were enriched by pfu DNA polymerase with "nest PCR" methods. These fragments were ligated into pBluescript SK (+) Phagemids vector with double endonuclease reaction sequentially. RESULTS: With endonuclease reaction and DNA sequencing, it was proved that the objective plasmid, Xukd-pbsk, was constructed correctively and the kanamycin resistance gene could be expressed in vitro. CONCLUSION: The S. mutans luxS gene allelic exchange plasmid is constructed correctively in this research and can be used in the future research of S. mutans luxS gene knockout mutant.

Bacterial Proteins↗

PubMed2006

Multiple exposures to chlorhexidine and xylitol: adhesion and biofilm formation by Streptococcus mutans.

Growing evidence from clinical studies suggests that mothers using xylitol gums or lozenges have decreased levels of Streptococcus mutans (SM) and do not transmit these cariogenic bacteria as readily to their children. To begin to determine mechanisms for these clinical findings and to explore potential synergism of antimicrobial combinations, we studied the effect of multiple exposures of chlorhexidine (CHX) combined with copper gluconate (CG) or zinc gluconate (ZG) followed by xylitol (XYL) on the ability of SM to adhere and form biofilms. Cell suspensions of SM were exposed two times to CHX; CG; CHX plus CG; ZG; and CHX plus ZG, and then four times to XYL. Control cells were exposed six times to water or XYL or received no treatment. For biofilm assessment, glass slides were inoculated with treated cells, and numbers of bacteria were enumerated after 48 hours of incubation. To assess the ability of SM to adhere, microtiter plate wells coated with primary S. sanguinis biofilms grown in sucrose were inoculated with treated SM, and adhesion was determined. Cells exposed to CHX-XYL combinations exhibited significant but transient inhibition of growth. The multiple-exposure regimen groups showed significant decreases in the ability of SM to form biofilms (P < 0.05). However, the CHX-XYL group exhibited a much greater effect than the other treatment groups (P < 0.001). Adhesion studies revealed that none of the multiple-exposure regimens had a significant effect on adhesion of SM to primary biofilms of S. sanguinis. We concluded that significant inhibition of SM growth and subsequent inability to grow as biofilms in the presence of sucrose occurs after a staggered exposure regimen to CHX initially and then to XYL. This may help explain the clinical data showing the decreased levels of SM in mothers treated with CHX and XYL.

Anti-Infective Agents, Local↗

PubMed1995

Streptococci and actinomyces inhibit regrowth of Streptococcus mutans on gnotobiotic rat molar teeth after chlorhexidine varnish treatment.

Clinical studies suggest that the long-term suppression of mutans streptococci on tooth surfaces after intensive chlorhexidine therapy is mainly due to bacterial interference. Other streptococci and also Actinomyces naeslundii are proposed to inhibit regrowth of mutans streptococci after suppression by the agent. We have tested this hypothesis in gnotobiotic rats associated with Streptococcus mutans alone, or associated with S. mutans and strains of Streptococcus oralis, Streptococcus sanguis, Streptococcus gordonii, Streptococcus mitis biovar I, and A. naeslundii. Left lower jaws in these rats were treated with concentrated chlorhexidine varnish, and the return of S. mutans on the treated jaws monitored. In mono-associated rats, S. mutans regained the level of the untreated right lower jaw in approximately 1 week. In contrast, S. mutans remained suppressed for several weeks in rats multi-associated with other streptococci and actinomyces strains. The suppression was more pronounced in the rats fed on basal diet with little free sugars than in rats fed on a sucrose-containing diet. Counts of other streptococci recovered quickly from the intensive chlorhexidine treatment, but A. naeslundii remained suppressed for at least 1 week. The findings demonstrate the crucial importance of the oral microflora in controlling regrowth of mutans streptococci after chemotherapy.

Actinomyces↗

PubMed1993

In vitro susceptibility of Streptococcus mutans to chlorhexidine and six other antimicrobial agents.

The susceptibility of Streptococcus mutans to chlorhexidine and to six commonly used, systemic antibacterial agents (amoxicillin, cefuroxime, penicillin, sulfamethoxazole-trimethoprim, tetracycline, and erythromycin) was studied for 424 clinical isolates from 116 children and students. The MIC of chlorhexidine for all isolates was < or = 1 micrograms/ml. No resistance to the other antimicrobial agents was detected. Although widely exposed to various antimicrobial agents, S. mutans has remained susceptible to common antimicrobial agents, most importantly to chlorhexidine.

Adult↗

PubMed1998

A medium-copy-number plasmid for insertional mutagenesis of Streptococcus mutans.

We have constructed a plasmid useful for insertional mutagenesis in Streptococcus mutans. The molecule, pSU20Erm, is based on a derivative of pACYC184 known as pSU20. The plasmid described here is approximately 3.7 kb in size and has the following properties: it replicates in Escherichia coli, does not replicate in S. mutans, contains an erythromycin-resistance marker which can be selected in E. coli or the streptococci, contains a multiple cloning site with few restriction sites in the remainder of the molecule, and can be screened on X-Gal-containing medium for the presence of insertions into the multiple cloning site. We have used the plasmid to construct a library of S. mutans DNA in E. coli and show that the clones can be reintegrated into the S. mutans chromosome via homologous recombination, thereby interrupting native genes. The plasmid has been used to clone part of a homologue of the E. coli drpA gene, encoding a global regulatory element for RNA synthesis. Further, we have identified an element closely linked to drpA in S. mutans with high homology to IS861.

Amino Acid Sequence↗

PubMed1997

Effects of antibodies against cell surface protein antigen PAc-glucosyltransferase fusion proteins on glucan synthesis and cell adhesion of Streptococcus mutans.

Cell surface protein antigen (PAc) and glucosyltransferases (GTFs) produced by Streptococcus mutans are considered to be major colonization factors of the organism, and the inhibition of these two factors is predicted to provide protection against dental caries. In this study, we have constructed fusion protein PAcA-GB, a fusion of the saliva-binding alanine-rich region (PAcA) of PAc with the glucan binding (GB) domain of GTF-I, an enzyme catalyzing the synthesis of water-insoluble glucan from sucrose, and fusion protein PAcA-SB, a fusion of PAcA with the sucrose binding (SB) domain of GTF-I. The recombinant fusion proteins were purified from cell extracts of Escherichia coli harboring the fusion genes, and rabbit antibodies against these fusion proteins were prepared. Water-insoluble glucan synthesis by cell-associated and cell-free GTF preparations from S. mutans as well as total glucan synthesis by GTF-I was markedly inhibited by anti-PAcA-GB immunoglobulin G (IgG) antibodies but not by anti-PAcA-SB IgG antibodies. Significant inhibition of the sucrose-independent and sucrose-dependent adhesion of S. mutans to saliva-coated hydroxyapatite beads was observed when anti-PAcA-GB antibodies were added to the reaction mixture. Anti-PAcA-SB antibodies inhibited the adhesion of S. mutans to the beads in the absence of sucrose but not in the presence of sucrose. Immunization with the fusion protein PAcA-GB may be useful for controlling the colonization of teeth by S. mutans.

Animals↗