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PubMed2005

Trigger factor in Streptococcus mutans is involved in stress tolerance, competence development, and biofilm formation.

Trigger factor is a ribosome-associated peptidyl-prolyl cis/trans isomerase that is highly conserved in most bacteria. A gene, designated ropA, encoding an apparent trigger factor homologue, was identified in Streptococcus mutans, the primary etiological agent of human dental caries. Inactivation of ropA had no major impact on growth rate in planktonic cultures under the conditions tested, although the RopA-deficient mutant formed long chains in broth. Deficiency of RopA decreased tolerance to acid killing and to oxidative stresses induced by hydrogen peroxide and paraquat, and it reduced transformation efficiency about 200-fold. Addition of synthetic competence-stimulating peptide to the culture medium enhanced transformability of both the mutant and wild-type strains, although the ropA strain did not attain levels of competence observed for the parent. Loss of RopA decreased the capacity of S. mutans to form biofilms by over 80% when cultivated in glucose, but it increased biofilm formation by over 50% when sucrose was provided as the carbohydrate source. Western blot analysis revealed that the expression of glucosyltransferases B and D was lower in the RopA-deficient mutant. These results suggest that RopA is a key regulator of acid and oxidative stress tolerance, genetic competence, and biofilm formation, all critical virulence properties of S. mutans.

Bacterial Proteins↗

PubMed2004

LuxS-mediated signaling in Streptococcus mutans is involved in regulation of acid and oxidative stress tolerance and biofilm formation.

LuxS-mediated quorum sensing has recently been shown to regulate important physiologic functions and virulence in a variety of bacteria. In this study, the role of luxS of Streptococcus mutans in the regulation of traits crucial to pathogenesis was investigated. Reporter gene fusions showed that inactivation of luxS resulted in a down-regulation of fructanase, a demonstrated virulence determinant, by more than 50%. The LuxS-deficient strain (TW26) showed increased sensitivity to acid killing but could still undergo acid adaptation. Northern hybridization revealed that the expression of RecA, SmnA (AP endonuclease), and Nth (endonuclease) were down-regulated in TW26, especially in early-exponential-phase cells. Other down-regulated genes included ffh (a signal recognition particle subunit) and brpA (biofilm regulatory protein A). Interestingly, the luxS mutant showed an increase in survival rate in the presence of hydrogen peroxide (58.8 mM). The luxS mutant formed less biofilm on hydroxylapatite disks, especially when grown in biofilm medium with sucrose, and the mutant biofilms appeared loose and hive-like, whereas the biofilms of the wild type were smooth and confluent. The mutant phenotypes were complemented by exposure to supernatants from wild-type cultures. Two loci, smu486 and smu487, were identified and predicted to encode a histidine kinase and a response regulator. The phenotypes of the smu486 smu487 mutant were, in almost all cases, similar to those of the luxS mutant, although our results suggest that this is not due to AI-2 signal transduction via Smu486 and Smu487. This study demonstrates that luxS-dependent signaling plays critical roles in modulating key virulence properties of S. mutans.

Bacterial Proteins↗

PubMed1980

Comparison of selective broth and plating methods for isolation of Streptococcus mutans from root surface dental plaques.

Approximately 150 sound root surfaces in 44 subjects prone to root surface caries were sampled longitudinally to determine the microbial flora associated with root caries initiation. During the first 16 months of the study, a comparison of Streptococcus mutans recovery was made by using three bacteriological media: mitis-salivarius agar (MSA), mitis-salivarius-bacitracin-sucrose agar (MSB), and a partially selective mannitol-containing broth. Total streptococcal and S. mutans populations were found to be much lower than in previous reports. MSB was more selective; S. mutans was detected in many samples when its numbers were too low for isolation on MSA. However, recovery of S. mutans was greater on MSA than on MSB for most samples yielding colonies on both media. Mannitol-containing broth used as an enrichment medium yielded the highest frequency of S. mutans isolation among the three media.

Aged↗

PubMed1982

Antibacterial action of condensed phosphates on the bacterium Streptococcus mutans and experimental caries in the hamster.

Condensed phosphates (CP: Na salts of pyro-, tripoly-, tetrapoly-, pentapoly-, hexameta- and ultra-; K salts of pyro- and poly-) used as food additives depressed the growth of seven strains of Streptococcus mutans (serotype a-g) as assessed by disc diffusion methods. Minimal inhibitory concentrations (MIC) of CP on growth of strain K1-R (g) in a chemically defined medium were measured turbidimetrically. Commercial grade CP (CP used) had the same growth inhibitory effects as purified linear type CP and they were superior to the cyclic type CP. The MIC of CP for Strep. mutans appeared to be related to their chelating capacity. As the growth inhibition by CP was reversed by the addition of divalent metal ions (Ca2+, Mg2+ or Mn2+), the chelating capacity of CP was apparently responsible for their antibacterial action. The antibacterial action of CP seemed largely bacteriostatic. Condensed phosphates depressed lactate production from glucose and sucrose by the cells of strain K1-R. A similar inhibition was produced by the supernatant of heated human saliva. Condensed phosphates depressed insoluble glucan production from sucrose by the cells of strain K1-R. The inhibition of sugar metabolism may be due to the interference of sugar transport into Strep. mutans induced by the chelation effects of CP. Hamsters were inoculated orally with strain K1-R and reared on the high-sucrose diet No. 2000 supplemented with 2 per cent (w/w) CP for 60 days. Dietary supplements of CP were associated with reduced caries activity (p less than 0.01) and plaque formation (p less than 0.05). The antibacterial actions of CP could be responsible for these caries-inhibitory effects.

Animals↗

PubMed1984

Comparison of polyvinyl chloride membrane electrodes sensitive to alkylphosphonium ions for the determination of the electrical difference (delta psi) of Streptococcus mutans and Lactobacillus casei.

Polyvinyl chloride membrane electrodes sensitive to tetraphenyl phosphonium (TPP+), butyltriphenyl phosphonium ( bTPP +), and methyltriphenyl phosphonium ( mTPP +) ions have been compared for the determination of the electrical potential difference (delta psi) of the oral bacteria, Streptococcus mutans DR0001 /6 and Lactobacillus casei RB1014 . All three types of electrode proved suitable for determining delta psi, although the TPP+-sensitive electrode was particularly susceptible to interference by protonmotive force (delta p) dissipators known to inhibit sugar uptake by the bacteria. The mTPP +-sensitive electrode was the least affected. Similarly, both strains had a high nonspecific binding capacity for TPP+ and bTPP + ions, and this increased for all three ions when the bacteria were heated to 80 degrees C for 1 h to abolish glucose uptake and metabolism. This heat-treatment procedure is therefore not a suitable control for determination of nonspecific binding to cells. However, 1% (v/v) toluene, 20 microM gramicidin, or 10 microM valinomycin effectively depolarized the bacteria without interfering with nonspecific binding. The ionophores were therefore used subsequently for the determination of nonspecific binding of the lipid-soluble cations. The mTPP + ion and corresponding electrode proved the most effective system, and delta psi values of -89 and -107 mV were obtained for S. mutans and L. casei, respectively, harvested from glucose-limited continuous cultures and incubated in 100 mM Hepes-KOH buffer (pH 7.0), containing 1 mM dithiothreitol and 10 mM glucose. Although the delta psi of S. mutans decreased significantly in the presence of Mes-KOH and potassium phosphate buffers at pH 7.0, it increased to -119 mV in Tris-HCl buffer (pH 7.0).(ABSTRACT TRUNCATED AT 250 WORDS)

Biological Transport, Active↗

PubMedDate not supplied

Inhibitory effect of antibacterial resin composite against Streptococcus mutans.

Dental resin composites with antibacterial activity may be useful for preventing the secondary caries frequently seen around restorations. Three types of silver-supported antibacterial materials (Novaron, Amenitop and AIS) inhibited the growth of the major oral pathogen Streptococcus mutans. Minimum inhibitory amounts in suspensions of Novaron, Amenitop and AIS against S. mutans were 40, 30 and 400 microg/ml, respectively. These antibacterial materials were incorporated into TEGDMA-UDMA-based light-activated resin composite, and the antibacterial activities of these composites were examined. Composites incorporating 5 wt% (N-5) or more of Novaron and 7 wt% (AM-7) or more of Amenitop inhibited the growth of S. mutans, whereas composites incorporating up to 10 wt% of AIS did not. No significant difference in either compressive or flexural strength was observed between the control and N-5 composites after 1 day and 6 months of storage in water. However, for AM-5 composite, there was a significant difference in either strength parameter between the two immersion periods. There was no or extremely little release of silver ions from the N-5 and AM-5 composites after 1 day or 6 months of immersion in water. These results indicated that a light-activated resin composite incorporating silver-supported antibacterial material such as Novaron may be clinically useful due to its inhibitory effect against S. mutans and favorable mechanical properties.

Analysis of Variance↗

PubMed2002

Characterization of the amino acids involved in substrate specificity of nonphosphorylating glyceraldehyde-3-phosphate dehydrogenase from Streptococcus mutans.

In order to address the molecular basis of the specificity of aldehyde dehydrogenase for aldehyde substrates, enzymatic characterization of the glyceraldehyde 3-phosphate (G3P) binding site of non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase (GAPN) from Streptococcus mutans has been undertaken. In this work, residues Arg-124, Tyr-170, Arg-301, and Arg-459 were changed by site-directed mutagenesis and the catalytic properties of GAPN mutants investigated. Changing Tyr-170 into phenylalanine induces no major effect on k(cat) and K(m) for d-G3P in both acylation and deacylation steps. Substitutions of Arg-124 and Arg-301 by leucine and Arg-459 by isoleucine led to distinct effects on K(m), on k(cat), or on both. The rate-limiting step of the R124L GAPN remains deacylation. Pre-steady-state analysis and substrate isotope measurements show that hydride transfer remains rate-determining in acylation. Only the apparent affinity for d-G3P is decreased in both acylation and deacylation steps. Substitution of Arg-459 by isoleucine leads to a drastic effect on the catalytic efficiency by a factor of 10(5). With this R459L GAPN, the rate-limiting step is prior to hydride transfer, and the K(m) of d-G3P is increased by at least 2 orders of magnitude. Binding of NADP leads to a time-dependent formation of a charge transfer transition at 333 nm between the pyridinium ring of NADP and the thiolate of Cys-302, which is not observed with the holo-wild type. Accessibility of Cys-302 is shown to be strongly decreased within the holostructure. The substitution of Arg-301 by leucine leads to an even more drastic effect with a change of the rate-limiting step similar to that observed for R459I GAPN. Taking into account the three-dimensional structure of GAPN from S. mutans and the data of the present study, it is proposed that 1) Tyr-170 is not essential for the catalytic event, 2) Arg-124 is only involved in stabilizing d-G3P binding via an interaction with the C-3 phosphate, and 3) Arg-301 and Arg-459 participate not only in d-G3P binding via interaction with C-3 phosphate but also in positioning efficiently d-G3P relative to Cys-302 within the ternary complex GAPN.NADP.d-G3P.

Amino Acid Sequence↗

PubMed1983

Role of primers in glucan synthesis by glucosyltransferases from Streptococcus mutans strain OMZ176.

The effects of isomaltosaccharides of various molecular weights (isomaltose to dextran T2000) on glucan synthesis by a water-soluble glucan-synthesizing glucosyltransferase enzyme (GTase-S) and a water-insoluble glucan-synthesizing enzyme (GTase-I), both from Streptococcus mutans OMZ176, were examined. The activity of GTase-S was not affected by the addition of the isomaltosaccharides, but GTase-I was stimulated increasingly by isomaltosaccharides with degrees of polymerization more than 10. The GTase-I activity first increased and thereafter decreased slightly with increasing amounts of a soluble dextran. Maximal stimulation occurred at concentrations in the range 0.1 to 0.2 mg ml-1, when dextran T10 was used as a primer. The rate of glucan synthesis was highly enhanced by the combined action of GTase-S and GTase-I. The profile of the net activity of GTase-I in the presence of various amounts of GTase-S was similar to that of GTase-I in the presence of increasing amounts of an exogenous dextran. These results collectively suggest that soluble glucan produced by GTase-S from sucrose acts as an intrinsic primer for the glucan synthesis by GTase-I, indicating the contribution of autopriming in glucan synthesis by crude GTase of S. mutans.

Dextrans↗

PubMed1995

[Adherence of the surface protein P(1) of Streptococcus mutans MT(6)R(Serotype C).].

In this study,the surface protein P(1) of Streptococcus mutans MT(6)R(Serotype C) was extracted from the culture supernants,purified by PAGE,identified by the standard antisera and labelled by with (131)I.The adherence of (131)I protein P(1)((131)I-P(1)) to the saliva-coated hydroxyaptite (S-HA) of the CF (caries-free,22,DFS=0) were studied.The adhesion of (131)I-P(1) to the S-HA promoted a greater extent than that to the HA treated with buffer and bovine serum albumin(P<0.01).This result suggested that protein P(1) may be one of the important adhesins of S.mutans.

English Abstract↗

PubMed1991

Effect of growth rate and pH on intracellular levels and activities of the components of the phosphoenolpyruvate: sugar phosphotransferase system in Streptococcus mutans Ingbritt.

The growth of Streptococcus mutants Ingbritt in continuous culture at low pH or high growth rates repressed the biosynthesis of the components of the phosphoenolpyruvate:sugar phosphotransferase system (PTS). The cellular concentrations of the soluble components HPr, enzyme I (EI), and EIII for mannose (IIIman) and EII activity for glucose, mannose, 2-deoxyglucose (2DG), and fructose were determined in membrane preparations from cells grown at pHs from 8.0 to 5.0 and at dilution (D) or growth rates from 0.1 to 1.0 h-1. The cellular levels of HPr and EI varied less than threefold under all of the growth conditions tested. On the other hand, EII activity in membranes from cells grown at D = 0.1 h-1 was repressed by growth at pHs below 8.0, with cells grown at pH 5.0 completely devoid of EII activity. In addition, cells grown at D = 0.5 and 1.0 h-1 exhibited little PTS activity for glucose, mannose, and 2DG and twofold-lower activity for fructose. These activities were stimulated by the addition of a membrane-free cytoplasmic fraction, and this activating activity was shown to be due to the presence of IIIman. Estimation of the cellular content of IIIman indicated that the synthesis of this factor was repressed by growth above and below pH 7.0 and was particularly sensitive to growth at high rates. These results indicate that with S. mutans Ingbritt, both pH and growth rate regulate the genes for the synthesis of EIIs involved in the phosphorylation of glucose, mannose, 2DG, and fructose and the gene for the formation of IIIman.

Bacterial Proteins↗

PubMed2000

Active detachment of Streptococcus mutans cells adhered to epon-hydroxylapatite surfaces coated with salivary proteins in vitro.

Although the formation of biofilms has been much studied, detachment of adherent cells from biofilms has been relatively neglected. Recent results have shown that adherent Streptococcus mutans cells can actively detach from epon-hydroxylapatite (EHA) rods conditioned with hog gastric mucin. The mechanisms for adherence and detachment of Strep. mutans cells in this system was uncertain. In the present study, resting Strep. mutans cells were used to form a simple monolayer on EHA rods coated with saliva and salivary agglutinin (SAG). Preliminary experiments defined the variables for conditioning EHA with saliva and SAG and establishing the adherence of Strep. mutans to the conditioned surfaces. The results showed that salivary proteins including SAG adsorbed rapidly to EHA and that a relatively stable Strep. mutans NG8 monolayer was formed within 60 min of incubation. The monolayers were subsequently used for detachment studies. The results showed that adherent Strep. mutans cells detached in a temperature-dependent manner and responded to the addition of a preparation of surface protein-releasing enzyme (SPRE) obtained from Strep. mutans in a dose-dependent fashion. The effect of the exogenous SPRE on detachment could be abrogated by pronase treatment. Two putative SPRE-defective mutants (A and E) were generated by Tn917 mutagenesis. Both mutants possessed a single transposon insertion as demonstrated by Southern hybridization and appeared to be different from one another based on the hybridization patterns. Mutant A displayed an increased quantity of cell-surface antigen P1, an adhesin that interacts with SAG. At the same time mutant A was unable to release P1 and other high molecular-weight proteins from the cell surface. Mutant A detached at a significantly lower rate (21%) than the parent strain (37%) (p=0.05). SPRE prepared from mutant A was unable to release Strep. mutans NG8 adherent cells as compared to SPRE obtained from the wild-type cells. Collectively, these results suggest that the detachment of Strep. mutans adherent cells formed on salivary protein-coated EHA was an active process mediated by the action of SPRE.

Adhesins, Bacterial↗

PubMed1984

Exchange of fluoride between bovine enamel and the surface-related cells of the oral bacterium Streptococcus mutans.

Standard areas of intact bovine enamel surface were fluoridated with dental F-varnish for 24 h and then cleaned from varnish residues and thoroughly rinsed with distilled water. Sucrose fermentation by a plaque-like layer of Streptococcus mutans cells covering such an enamel surface was accompanied by a rapid but transient accumulation of F of enamel origin by the Strep. mutans cells and by a pH drop in the plaque to pH 4.0. The uptake of F from the surface by the control cells, utilizing their carbohydrate stores and causing a smaller pH-drop, was slow but no release of F back to the cell exterior took place within 18 h. In a second experiment, F- varnished and placebo- varnished bovine enamel granules were used as above, but they were not thoroughly washed after being varnish-treated and cleaned. Both the sucrose-fermenting and the control layer of Strep. mutans rapidly released appreciable but equal amounts of fluoride from the F-treated enamel. The accumulation of F of enamel origin by the Strep. mutans cells with or without sucrose was rapid and of almost the same magnitude. In the model with the sucrose-utilizing Strep. mutans and the F-treated enamel granules, the plaque pH-drop was less and the dissolution of the enamel Ca and P completely prevented compared to the respective changes in the sucrose-utilizing model with placebo-treated enamel granules.

Animals↗

PubMed2005

Evaluation of oxazaborolidine activity on Streptococcus mutans biofilm formation.

Dental diseases are among the most prevalent afflictions of humankind. These diseases are associated with the formation of biofilms harbouring pathogenic bacteria. Eight different derivatives of oxazaborolidines were synthesised and evaluated for their affect on Streptococcus mutans adhesion and biofilm formation. Structure-activity relationship was observed. The B-butyl moiety of the oxazaborolidines contributed an anti-adhesion effect for all derivatives, whilst its effect diminished when the boron atom was incorporated in a fused heterocyclic ring. The B-phenyl group induced bacterial adhesion in all tested compounds Oxazaborolidines may serve as novel agents for affecting oral biofilm formation. Moreover, the ability to alter the oxazaborolidine molecule and thus affect biofilms offers an excellent opportunity to study biofilm formation.

Anti-Bacterial Agents↗

PubMed1995

Correlating Streptococcus mutans counts in saliva with plaque amount, gingival inflammation and caries experience in school children.

Samples of stimulated whole saliva were obtained from ninety-four 12-14-year-old school children living in inner London to evaluate if there was a correlation between Streptococcus mutans counts in saliva with plaque amount, gingival inflammation and caries experience. S. mutans counts were obtained by a dip-slide method (Dentocult 'Strip Mutans') in which the count was expressed as 0, 1, 2, 3, or 4 based on visual estimation of the colony density. There was no association between counts' of S. mutans in saliva with plaque amount and gingival inflammation. However, there was a significant trend of increased decayed, missing, filled surfaces (DMFS) with increasing S. mutans counts.

Adolescent↗

PubMed1991

The efficacy of chlorhexidine gel in reduction of Streptococcus mutans and Lactobacillus species in patients treated with radiation therapy.

Xerostomia may develop in patients with cancer who receive radiotherapy that includes the salivary glands in the field. These patients are at high risk of rampant dental caries. Streptococcus mutans and Lactobacillus species have been associated with dental caries. Quantitative counts of these organisms demonstrated high caries risk due to streptococci in 66% and due to lactobacilli in 100% of patients studied. Use of chlorhexidine rinse was shown to reduce S. mutans counts 1.1 logs and lactobacilli 1.1 logs. The use of chlorhexidine gel resulted in a reduction of S. mutans 1.2 logs and lactobacilli 2.2 logs. In the subjects using the rinse, caries risk due to streptococci was reduced to low levels in 44% and due to lactobacilli in only one subject, with reduction to moderate risk in one third and no change in risk in the remaining patients. The use of chlorhexidine gel was found to reduce the caries risk associated with streptococci to low levels in all patients, and the risk associated with lactobacilli to low and moderate risk in two thirds of patients.

Adult↗

PubMed1994

The effect of milk and casein proteins on the adherence of Streptococcus mutans to saliva-coated hydroxyapatite.

Experiments sought to determine the nature of the binding of milk proteins to hydroxyapatite (HA) and to saliva-coated hydroxyapatite (sHA), and to determine the effect of milk and casein on the adherence of Streptococcus mutans GS-5 to sHA. The binding of radiolabelled alpha-casein to HA was reduced when incubated simultaneously with parotid saliva, and enhanced in the presence of milk. The binding of beta- and kappa-casein to HA was unaffected by the presence of parotid saliva and enhanced by the presence of milk. The in vitro bacterial adherence of Strep. mutans GS-5 to sHA beads was reduced when beads were coated with milk instead of buffer, or when bacteria were added to sHA in the presence of milk instead of buffer. Casein proteins (alpha, beta, kappa) added to sHA simultaneously with bacteria inhibited the adherence of Strep. mutans GS-5 to sHA. kappa-Casein, when bound to sHA, inhibited streptococcal adherence to sHA; alpha- and beta-casein, when bound to sHA, had no effect on streptococcal adherence. Fractionation of kappa-casein by anion-exchange chromatography revealed the anti-adherence activity of kappa-casein was mediated primarily by a 40,000 mol. wt. glycoprotein-containing fraction. These data show that milk, particularly kappa-casein fractions, can modulate the adherence of Strep. mutans GS-5 to SHA surfaces in vitro.

Adult↗

PubMed1999

Protective immunity against Streptococcus mutans infection in mice after intranasal immunization with the glucan-binding region of S. mutans glucosyltransferase.

Here we present the construction and characterization of a chimeric vaccine protein combining the glucan-binding domain (GLU) of the gtfB-encoded water-insoluble glucan-synthesizing glucosyltransferase enzyme (GTF-I) from Streptococcus mutans and thioredoxin from Escherichia coli, which increases the solubility of coexpressed recombinant proteins and stimulates proliferation of murine T cells. The protective potential of intranasal (i.n.) immunization with this chimeric immunogen was compared to that of the GLU polypeptide alone in a mouse infection model. Both immunogens were able to induce statistically significant mucosal (salivary and vaginal) and serum responses (P < 0.01) which were sustained to the end of the study (experimental day 100). Following infection with S. mutans, sham-immunized mice maintained high levels of this cariogenic organism ( approximately 60% of the total oral streptococci) for at least 5 weeks. In contrast, animals immunized with the thioredoxin-GLU chimeric protein (Thio-GLU) showed significant reduction (>85%) in S. mutans colonization after 3 weeks (P < 0.05). The animals immunized with GLU alone required 5 weeks to demonstrate significant reduction (>50%) of S. mutans infection (P < 0.05). Evaluation of dental caries activity at the end of the study showed that mice immunized with either Thio-GLU or GLU had significantly fewer carious lesions in the buccal enamel or dentinal surfaces than the sham-immunized animals (P < 0.01). The protective effects against S. mutans colonization and caries activity following i.n. immunization with GLU or Thio-GLU are attributed to the induced salivary immunoglobulin A (IgA) anti-GLU responses. Although in general Thio-GLU was not significantly better than GLU alone in stimulating salivary IgA responses and in protection against dental caries, the finding that the GLU polypeptide alone, in the absence of any immunoenhancing agents, is protective against disease offers a promising and safe strategy for the development of a vaccine against caries.

Administration, Intranasal↗

PubMed1993

Streptococcus mutans fructosyltransferase (ftf) and glucosyltransferase (gtfBC) operon fusion strains in continuous culture.

Three glucosyltransferases (GTFs), which catalyze the formation of water-insoluble adherent glucans, and fructosyltransferase (FTF), which synthesizes fructans, are believed to contribute to the pathogenic potential of Streptococcus mutans. Study of the regulation of expression of GTF and FTF has been difficult because of the complexity and number of exoenzymes produced by this bacterium. By using continuous chemostat culture to control environmental conditions, chloramphenicol acetyltransferase (CAT) operon fusions were utilized to measure transcriptional activity of the ftf and gtfBC gene promoters. Expression of these operon fusions was differentially regulated in response to culture pH and growth rate and during transition states between growth domains. Furthermore, the addition of sucrose to steady-state cultures resulted in significant increases in CAT specific activities for both fusions. In a few cases, GTF and FTF enzyme specific activities did not parallel those of the corresponding CAT fusion activities; this lack of correspondence was likely due to posttranscriptional events controlling enzyme secretion and enzyme activity, as well as to the differential expression of dextranase(s) and fructan hydrolase by S. mutans. These results clearly demonstrate that the extracellular polymer synthesis machinery of S. mutans is regulated in a complex manner. The use of operon fusions in combination with chemostat culture is a viable approach to analyzing gene expression in S. mutans and will be helpful in defining the molecular mechanisms underlying regulation of expression of virulence attributes under conditions that may more closely mimic those in dental plaque.

Extracellular Space↗