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PubMed1978

Asymmetrical dental caries and Streptococcus mutans infection.

A 27-year-old woman chewed unilaterally and had restorations and caries only on the right side of the dentition. The left side had a greater amount of soft and hard deposits and more severe periodontal disease. Plaque samples from occlusal and interproximal tooth surfaces were collected and cultured. The proportion of Streptococcus mutans of the total anaerobic count in the plaque samples from the right side was 1,000 to 10,000 times as high as from the left side. The proportion of S mutans of the total streptococcus was 6% to 20% on the right and less than 1% on the left side.

Adult↗

PubMed1998

Identification of a homolog of CcpA catabolite repressor protein in Streptococcus mutans.

A locus containing a gene with homology to ccpA of other bacteria has been cloned from Streptococcus mutans LT11, sequenced, and named regM. Upstream of the regM gene, on the opposite strand, is a gene encoding an X-Pro dipeptidase, pepQ. A 14-bp palindromic sequence with homology to the consensus catabolite-responsive element sequence lay in the promoter region between the two genes. To study the function of regM, the gene was inactivated by insertion of an antibiotic resistance marker. Diauxic growth of S. mutans on a number of sugars in the presence of glucose was not affected by disruption of regM. The loss of RegM increased glucose repression of alpha-galactosidase, mannitol-1-P dehydrogenase, and P-beta-galactosidase activities. These results suggest that while RegM can affect catabolite repression in S. mutans, it does not conform to the model proposed for CcpA in Bacillus subtilis.

Amino Acid Sequence↗

PubMed1991

Salivary-agglutinin-mediated adherence of Streptococcus mutans to early plaque bacteria.

Interspecies binding is important in the colonization of the oral cavity by bacteria. Streptococcus mutans can adhere to other plaque bacteria, such as Streptococcus sanguis and Actinomyces viscosus, and this adherence is enhanced by saliva. The salivary and bacterial molecules that mediate this interaction were investigated. Salivary agglutinin, a mucinlike glycoprotein known to mediate the aggregation of many oral streptococci in vitro, was found to mediate the adherence of S. mutans to S. sanguis or A. viscosus. Adherence of S. mutans to saliva- or agglutinin-coated S. sanguis and A. viscosus was inhibited by antibodies to the bacterial agglutinin receptor. Expression of the S. sanguis receptor (SSP-5) gene in Enterococcus faecalis increased adhesion of this organism to saliva- or agglutinin-coated S. sanguis and A. viscosus. This interaction could be inhibited by antibodies to the agglutinin receptor. The results suggest that salivary agglutinin can promote adherence of S. mutans to S. sanguis and A. viscosus through interactions with the agglutinin receptor on S. mutans.

Agglutinins↗

PubMed2004

Application of in vitro mutagenesis to identify the gene responsible for cold agglutination phenotype of Streptococcus mutans.

A previously unidentified protein with an apparent molecular mass of 120 kDa was detected in some Streptococcus mutans strains including the natural isolate strain Z1. This protein was likely involved in the cold-agglutination of the strain, since a correlation between this phenotype and expression of the 120 kDa protein was found. We have applied random mutagenesis by in vitro transposition with the Himar1 minitransposon and isolated three cold-agglutination-negative mutants of this strain from approximately 2,000 mutants screened. A 2.5 kb chromosomal fragment flanking the minitransposon in one of the three mutants was amplified by PCR-based chromosome walking and the minitransposon insertion in the other two mutants occurred also within the same region. Nucleotide sequencing of the region revealed a 1617 nt open reading frame specifying a putative protein of 538 amino acid residues with a calculated molecular weight of 57,192. The deduced eight amino acid sequence following a putative signal sequence completely coincided with the N-terminal octapeptide sequence of the 120 kDa protein determined by the Edman degradation. Therefore, the 1617 nt gene unexpectedly encoded the 120 kDa protein from S. mutans. Interestingly, this gene encoded a collagen adhesin homologue. In vitro mutagenesis using the Himar1 minitransposon was successfully applied to S. mutans.

Agglutination↗

PubMed1999

Recombination between gtfB and gtfC is required for survival of a dTDP-rhamnose synthesis-deficient mutant of Streptococcus mutans in the presence of sucrose.

The rml genes are involved in dTDP-rhamnose synthesis in Streptococcus mutans. A gene fusion between gtfB and gtfC, which both encode extracellular water-insoluble glucan-synthesizing enzymes, accompanied by inactivation of the rml genes was observed for cells grown in the presence of sucrose. The survival rates of rml mutants isolated in the absence of sucrose were drastically reduced in the presence of sucrose. The rates were consistent with the frequency of spontaneous gene fusions between gtfB and gtfC, suggesting that the spontaneous recombinant organisms were selected in the presence of sucrose. The rml mutants with a gtfB-gtfC fusion gene had markedly reduced water-insoluble glucan synthetic activity and lost the ability to colonize glass surfaces in the presence of sucrose. These results suggest that the rml mutants of S. mutans, which are defective in dTDP-rhamnose synthesis, can survive only in the absence of water-insoluble glucan synthesis.

Gene Expression Regulation, Bacterial↗

PubMed1994

Vesicles prepared from Streptococcus mutans demonstrate the presence of a second glucose transport system.

Streptococcus mutans, an important aetiological agent of dental caries, is known to transport glucose via the phosphoenolpyruvate (PEP) phosphotransferase system (PTS). An alternative non-PTS glucose transport system in S. mutans Ingbritt was suggested by the increased ATP-dependent phosphorylation of glucose and the presence of higher cellular concentrations of free glucose in cells grown in continuous culture under PTS-repressed conditions compared to those resulting in optimal PTS activity. A method was developed for the preparation of membrane vesicles in order to study this system in the absence of PTS activity. These vesicles had very low activity of the cytoplasmic enzymes, glucokinase, pyruvate kinase and lactate dehydrogenase. This, coupled with the lack of glycolytic activity and the inability to transport glucose, suggested that the vesicles would also be deficient in PTS activity because of the absence of the general soluble PTS proteins, Enzyme I and HPr, required for the transport of all PTS sugars. Freeze-fracture electron microscopy and membrane H(+)-ATPase analysis indicated that over 90% of the vesicles had a right-side-out orientation. Vesicles from cells grown in continuous culture under PTS-dominant and PTS-repressed conditions both exhibited glucose counterflow. This indicates the presence of a constitutive non-PTS carrier in the organism capable of transporting glucose and utilizing ATP for glucose phosphorylation. Analysis of growth yields of cells grown under PTS-repressed and PTS-optimal conditions suggests that ATP, or an equivalent high energy molecule, must be involved in the actual transport process. This analysis is consistent with an ATP-binding protein model such as the Msm transport system reported by R. R. B. Russell and coworkers (J Biol Chem 267, 4631-4637), but it does not exclude the possibility of a separate permease for glucose.

Adenosine Triphosphate↗

PubMed1989

Streptococcus mutans infection level and caries in a group of 5-year-old children.

The level of Streptococcus mutans in stimulated saliva and its association with caries experience was evaluated in 149 5-year-old children. In general, salivary S. mutans levels were low, and it was detected only in 46% of saliva samples. There was, however, a clear association between salivary levels of S. mutans and caries experience (chi 2 = 53.65, p less than 0.001). Salivary examination was supplemented with plaque samples in 47 children. The number of S. mutans positive surfaces increased with increasing salivary levels. S. mutans was most often isolated and comprised the highest proportion in the approximal samples. The number of children with high salivary S. mutans levels was very low (6%) when taken into account that 13% of the children were fairly caries active (dmfs greater than or equal to 5). This most probably means that in evaluation of caries risk, the salivary S. mutans screening level is different in preschool children and in older children. The level should be determined in longitudinal studies before applying to preschool children.

Bacteriological Techniques↗

PubMed1981

Lymphoid cell responses to bacterial cell wall components: mitogenic responses of murine B cells to Streptococcus mutans carbohydrate antigens.

The mitogenic activity of various purified serotype carbohydrate and cell wall lysate fractions of Streptococcus mutans for murine lymphocytes has been determined. The highest mitogenic responses occurred after 48 hr of stimulation with these carbohydrate preparations when tested on splenic cultures derived from C3H/HeJ and BALB/c mice. The response pattern obtained with optimum concentrations of these preparations was very similar to that seen with the B cell mitogen, LPS. A purified serotype g carbohydrate (M1 g) prepared by mutanolysin enzyme treatment of S. mutans 6715 cell walls stimulated good mitogenic responses in BALB/c nude and nu/+ splenic cultures, suggesting an effect on mouse B cells. This was further substantiated by studies showing that this antigen also induced responses in cultures of B cells purified by nylon wool fractionation, whereas purified T cells did not respond. Mitogenic responses were due to the carbohydrate moiety and not to possible LPS contamination, since alkaline treatment or mixture with polymyxin B greatly reduced responses to LPS; however, no alteration of mitogenic responses to M1 g occurred. Further, LPS nonresponsive C3H/HeJ spleen cells yielded good mitogenic responses to M1 g. On the other hand, periodate treatment, which is known to decompose carbohydrate moieties completely abrogated the mitogenic activity of M1 g antigen. Additional studies with serotypes c and e carbohydrate, which also induced mitogenic responses, suggested that this activity for lymphoid cells may be a common property of S. mutans cell wall carbohydrate.

Animals↗

PubMed1976

Activity of two Streptococcus mutans bacteriocins in the presence of saliva, levan, and dextran.

The extracellular dextrans produced from sucrose by Streptococcus mutans strains BHT and GS-5 did not prevent the synthesis or release of active bacteriocins by these two strains. In addition, several streptococci that were genetically sensitive to these bacteriocins, and that could synthesize a variety of extracellular dextrans and levans from sucrose, remained phenotypically sensitive when grown in the presence of sucrose. Bacteriocin activity was not altered by treatment with high-molecular-weight dextran or by human saliva. The bacteriocins produced by, and active against, S. mutans thus appear to be capable of acting in vivo and may play a role in regulating the bacterial ecology of the oral cavity.

Bacteriocins↗

PubMed2002

Analyses of Streptococcus mutans in saliva with species-specific monoclonal antibodies.

Three species-specific monoclonal antibodies (MAbs) against Streptococcus mutans were used to detect and quantify S. mutans levels in saliva. This study shows that MAb-based salivary S. mutans tests exhibit significantly higher specificity and sensitivity than the commonly used selective culture method. Examination of nearly 2,000 human saliva samples shows that S. mutans counts in human saliva vary from less than 10,000 to a high 36 million cells/mL. Over 15% of the saliva samples examined have salivary S. mutans counts over 500,000 cells/mL. When saliva samples were collected at different time points during a day, the number of salivary S. mutans in the same human subject varied, especially before and after sugar uptake. Additionally, data obtained from stimulated versus unstimulated saliva in the same human subjects differed greatly and appear to be completely uncorrelated. This study provides useful information and tools for analyzing the role of S. mutans in human dental caries.

Antibodies, Bacterial↗

PubMed2006

The SloR/Dlg metalloregulator modulates Streptococcus mutans virulence gene expression.

Metal ion availability in the human oral cavity plays a putative role in Streptococcus mutans virulence gene expression and in appropriate formation of the plaque biofilm. In this report, we present evidence that supports such a role for the DtxR-like SloR metalloregulator (called Dlg in our previous publications) in this oral pathogen. Specifically, the results of gel mobility shift assays revealed the sloABC, sloR, comDE, ropA, sod, and spaP promoters as targets of SloR binding. We confirmed differential expression of these genes in a GMS584 SloR-deficient mutant versus the UA159 wild-type progenitor by real-time semiquantitative reverse transcriptase PCR experiments. The results of additional expression studies support a role for SloR in S. mutans control of glucosyltransferases, glucan binding proteins, and genes relevant to antibiotic resistance. Phenotypic analysis of GMS584 revealed that it forms aberrant biofilms on an abiotic surface, is compromised for genetic competence, and demonstrates heightened incorporation of iron and manganese as well as resistance to oxidative stress compared to the wild type. Taken together, these findings support a role for SloR in S. mutans adherence, biofilm formation, genetic competence, metal ion homeostasis, oxidative stress tolerance, and antibiotic gene regulation, all of which contribute to S. mutans-induced disease.

Bacterial Adhesion↗

PubMed2004

Development of a PCR method for rapid identification of new Streptococcus mutans serotype k strains.

In a previous study, we isolated and characterized a new serotype k of Streptococcus mutans from human blood and oral cavities. Analysis of the genes involved in biosynthesis of the serotype-specific polysaccharide of serotype k strains revealed that the serotype k-specific nucleotide alignment was commonly present in the 5' region of the rgpF gene (350 bp from the initial sequence) compared to the reference strains, and then a method for rapid identification of serotype k strains was developed by use of PCR with primers designed on the basis of the sequence of the variable region. PCR assays with primers specific for amplification of serotype k strains showed a negative reaction with serotype c, e, and f strains and a positive reaction with serotype k strains, with the sensitivity for identification of the serotype k strains shown to range from 5 to 50 cells. Next, the frequency of positive reactions for serotype k-specific primers was surveyed with DNA taken from saliva samples from 200 subjects (2 to 18 years of age), and 10 of those showed a positive reaction, which was higher than the frequency in our previous survey with a serological method. In addition, all saliva samples from subjects with serotype k strains in our previous study were shown to be positive with the serotype k-specific primers. These results indicate that this new PCR method is effective for identification of subjects with S. mutans serotype k.

Adolescent↗

PubMed2005

Anticariogenic activity of macelignan isolated from Myristica fragrans (nutmeg) against Streptococcus mutans.

The occurrence of dental caries is mainly associated with oral pathogens, especially cariogenic Streptococcus mutans. Preliminary antibacterial screening revealed that the extract of Myristica fragrans, widely cultivated for the spice and flavor of foods, possessed strong inhibitory activity against S. mutans. The anticariogenic compound was successfully isolated from the methanol extract of M. fragrans by repeated silica gel chromatography, and its structure was identified as macelignan by instrumental analysis using 1D-NMR, 2D-NMR and EI-MS. The minimum inhibitory concentration (MIC) of macelignan against S. mutans was 3.9 microg/ml, which was much lower than those of other natural anticariogenic agents such as 15.6 microg/ml of sanguinarine, 250 microg/ml of eucalyptol, 500 microg/ml of menthol and thymol, and 1000 microg/ml of methyl salicylate. Macelignan also possessed preferential activity against other oral microorganisms such as Streptococcus sobrinus, Streptococcus salivarius, Streptococcus sanguis, Lactobacillus acidophilus and Lactobacillus casei in the MIC range of 2-31.3 microg/ml. In particular, the bactericidal test showed that macelignan, at a concentration of 20 microg/ml, completely inactivated S. mutans in 1 min. The specific activity and fast-effectiveness of macelignan against oral bacteria strongly suggest that it could be employed as a natural antibacterial agent in functional foods or oral care products.

Anti-Bacterial Agents↗

PubMed2004

Demonstration of Streptococcus mutans with a cell wall polysaccharide specific to a new serotype, k, in the human oral cavity.

Streptococcus mutans organisms are occasionally isolated from the blood of patients with infective endocarditis, though the mechanisms of invasion and survival remain to be elucidated. Two of four blood isolates from patients with bacteremia or infective endocarditis (strains TW295 and TW871) were serologically untypeable by immunodiffusion testing, which was due to a lack of the glucose side chain of the serotype-specific polysaccharide antigen of S. mutans. Immunodiffusion analyses using antisera against these strains demonstrated that 2 of 100 isolates from 100 subjects showed a positive reaction, while further analysis of 2500 isolates from 50 subjects revealed that all 50 isolates from a single subject were not reactive with anti-c, -e, and -f antisera, though they were reactive with anti-TW295 and -TW871 antisera. The oral isolates showed biological properties similar to those of the reference S. mutans strain MT8148, including high levels of sucrose-dependent adhesion and cellular hydrophobicity, along with expression of glucosyltransferases and a protein antigen, PA. We designated these organisms serotype k. A glucose side chain-defective mutant strain was then constructed by insertional inactivation of the gluA gene of strain MT8148, which showed biological properties similar to those of serotype k of S. mutans. Serotype k oral isolates were less susceptible to phagocytosis, as were the gluA-inactivated mutant of strain MT8148 and blood isolates. These results indicate that S. mutans serotype k strains are present in the oral cavity in humans and may be able to survive longer in blood owing to their low susceptibility to phagocytosis.

Adolescent↗

PubMed1980

Streptococcus mutans adherence: presumptive evidence for protein-mediated attachment followed by glucan-dependent cellular accumulation.

Adherence of Streptococcus mutans to smooth surfaces has been attributed to the production of sucrose-derived d-glucans. However, several studies indicate that the bacterium will adhere in the absence of sucrose. The present data confirmed that S. mutans adherence to saliva-coated hydroxyapatite beads in the absence of sucrose is described by the Langmuir equation. The nature of the sucrose-independent adherence was studied with the Persea americana agglutinin as a selective adherence inhibitor. Pretreatment of the bacterium with P. americana agglutinin caused a 10-fold reduction in adherence, and the inhibition was not reversed with the addition of sucrose. Pretreatment of S. mutans with proteases also reduced adherence, regardless of the sucrose content, whereas periodate oxidation and glucanohydrolase treatment of the bacteria reduced sucrose-mediated adherence to the levels found for sucrose-independent adherence. The P. americana agglutinin, glucanohydrolase, and pepsin pretreatment of the cells did not eliminate sucrose-induced agglutination. Scanning electron microscopy showed that short streptococcal chains were bound to saliva-coated hydroxyapatite crystals in the sucrose-independent system, whereas the presence of sucrose caused larger bacterial clumps to be found. A two-reaction model of S. mutans adherence was developed from these data. It is proposed that one reaction is attachment to the tooth pellicle which is mediated by cell-surface proteins rather than glucans or teichoic acids. The other reaction is cellular accumulation mediated by sucrose-derived d-glucans and cell surface lectins. A series of sequential adherence experiments with P. americana agglutinin as a selective inhibitor provided presumptive evidence for the validity of our model of S. mutans adherence.

Adsorption↗

PubMed1984

Natural antibodies in man to a protein antigen from the bacterium Streptococcus mutans related to dental caries experience.

Serum antibodies to a cell-wall protein antigen derived from Streptococcus mutans (SA I/II) were examined in 108 subjects by a solid-phase radioimmunoassay. As a control, antibodies to lipoteichoic acid and to Strep. mutans whole cells were examined and the relationship to dental caries of isotype-specific antibodies to both antigens determined. Serum-IgG antibodies to SA I/II and to Strep. mutans were significantly greater in subjects of low caries experience than in subjects of high caries experience, whereas serum-IgG antibodies to LTA showed no relationship. Serum-IgM antibodies to SA I/II were depressed in subjects with carious lesions, whereas IgM antibodies to Strep. mutans in the same subjects were raised. IgA antibodies against any antigen were not related to caries. Serum antibodies of each isotype to SA I/II were generally positively-correlated with antibodies to LTA but inhibition experiments demonstrated specificity of antibodies for each antigen. The relationship between antibodies to SA I/II and dental caries are consistent with those reported with antibodies to whole cells of Strep. mutans and suggest that high-serum IgG antibodies to SA I/II may be associated with protection against dental caries in man.

Adolescent↗

PubMed1998

Deletion of the central proline-rich repeat domain results in altered antigenicity and lack of surface expression of the Streptococcus mutans P1 adhesin molecule.

Members of the family of surface adhesins of oral streptococci, including P1 of Streptococcus mutans, contain two highly conserved repeat domains, one rich in alanine (A region) and the other rich in proline (P region). To assess the contribution of the P region to the biological properties of P1, an internal deletion in spaP was engineered. In addition, the P region was subcloned and expressed as a fusion partner with the maltose binding protein of Escherichia coli and liberated by digestion with factor Xa. Results of Western blot experiments in which recombinant polypeptides were probed with a panel of 11 monoclonal antibodies indicated that the P region is a necessary component of conformational epitopes within the central portion of P1. Antibodies reactive with the P region were detected in a polyclonal rabbit antiserum generated against whole S. mutans cells but not in two rabbit antisera generated against purified P1 (Mr approximately 185,000), suggesting that this domain is immunogenic on the surface of intact bacteria but not as part of a soluble full-length molecule. Finally, transformation of a spaP-negative mutant with a shuttle vector containing an internally deleted spaP lacking P-region DNA resulted in a complete absence of surface-localized P1 and substantially less P1 in sonicated cells compared to the case for the mutant complemented with the full-length gene. These results suggest that the P region is an integral component contributing to the conformation of the central region of P1 and indicate that its presence is necessary for surface expression of the molecule on S. mutans.

Adhesins, Bacterial↗

PubMed2000

Multiple stress responses in Streptococcus mutans and the induction of general and stress-specific proteins.

The authors have previously demonstrated that Streptococcus mutans shows an exponential-phase acid-tolerance response following an acid shock from pH 7.5 to 5.5 that enhances survival at pH 3.0. In this study the response of S. mutans H7 to acid shock was compared with the responses generated by salt, heat, oxidation and starvation. Prior induction of the acid-tolerance response did not cross-protect the cells from a subsequent challenge by the other stresses; however, prior adaptation to the other stresses, except heat (42 degrees C), protected the cells during a subsequent acid challenge at pH 3.5. Starvation by fivefold dilution of the basal medium (BM) plus fivefold reduction of its glucose content increased the numbers of survivors 12-fold, whereas elimination of glucose from fivefold-diluted BM led to a sevenfold enhancement compared to the control cells; this indicated a relationship between the acid and starvation responses. The stress responses were further characterized by comparing the 2D electrophoretic protein profiles of exponential-phase cells subjected to the various stress conditions. Cells were grown to exponential phase at pH 7.5 (37 degrees C) and then incubated for 30 min under the various stress conditions in the presence of 14C-labelled amino acids followed by cell extraction, protein separation by 2D gel electrophoresis and image analysis of the resulting autoradiograms. Using consistent twofold or greater changes in IOD % as a measure, oxidative stress resulted in the upregulation of 69 proteins, 15 of which were oxidation-specific, and in the downregulation of 24 proteins, when compared to the control cells. An acid shock from pH 7.5 to 5.5 enhanced synthesis of 64 proteins, 25 of them acid-specific, while 49 proteins exhibited diminished synthesis. The dilution of BM resulted in the increased formation of 58 proteins, with 11 starvation-specific proteins and 20 showing decreased synthesis. Some 52 and 40 proteins were enhanced by salt and heat stress, with 10 and 6 of these proteins, respectively, specific to the stress. The synthesis of a significant number of proteins was increased by more than one, but not all stress conditions; six proteins were enhanced by all five stress conditions and could be classified as general stress proteins. Clearly, the response of S. mutans to adverse environmental conditions results in complex and diverse alterations in protein synthesis to further cell survival.

Autoradiography↗