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PubMed1990

Carboxyl-terminal deletion analysis of the Streptococcus mutans glucosyltransferase-I enzyme.

Sequential deletion of the carboxyl-terminal amino acids (including the six direct repeating units) of the glucosyltransferase-I (GTF-I) enzyme of Streptococcus mutans revealed differential effects on sucrase and GTF activities. Removal of all but one repeating unit resulted in a truncated enzyme with significant sucrase activity but no detectable GTF activity. These results are compatible with the presence of two functional domains in the enzyme.

Amino Acid Sequence↗

PubMed1977

Binding of lectins to Streptococcus mutans cells and type-specific polysaccharides, and effect on adherence.

The lectin concanavalin A (Con A) agglutinated the cells of 13 of 15 strains of the seven serotypes of Streptococcus mutans in an 18-h incubation period. Strains of types a, d, f, and g agglutinated within 2 h. Strains of a, d, and f were also agglutinated in 2 h by the castor bean lectin RCA. S. sanguis, S. salivarius, S. bovis, Actinomyces viscosus, A. naeslundii, and Lactobacillus plantarum were agglutinated within 2 h. The S. mutans type f polysaccharide was precipitated by Con A. The a, b, c, d, and e polysaccharides were not precipitated. Glucan from d and e strains of S. mutans and dextran T2000 were also precipitated by Con A. D-glucose inhibited the agglutination of type f cells by Con A and the agglutination of type d cells by D-galactose. The quantity of [acetyl-3H]Con A bound was not proportional to the degree of agglutination. Cells grown in sucrose medium bound more Con A than those grown in glucose medium. After treatment with dextranase, the sucrose-grown cells bound two- to fourfold more Con A. The binding of Con A to the type-specific polysaccharide or to teichoic acid could not be determined by the use of specific antibody due to the binding of Con A to the antibody globulin on the cell surface. Con A bound to S. mutans cells did not inhibit the activity of cell-bound glucosyltransferase, glucan synthesis, and in vitro adherence. Bound Con A also did not inhibit the ability of heat-treated cells to bind glucosyltransferase, synthesize glucan, and produce in vitro adherence.

Agglutination↗

PubMed2006

Differential expression profiles of Streptococcus mutans ftf, gtf and vicR genes in the presence of dietary carbohydrates at early and late exponential growth phases.

Dental caries is one of the most common infectious diseases that affects humans. Streptococcus mutans, the main pathogenic bacterium associated with dental caries, produces a number of extracellular sucrose-metabolizing enzymes, such as glucosyltransferases (GTFB, GTFC and GTFD) and fructosyltransferase (FTF). The cooperative action of these enzymes is essential for sucrose-dependent cellular adhesion and biofilm formation. A global response regulator (vicR) plays important roles in S. mutans ftf and gtf expression in response to a variety of stimuli. A real-time reverse-transcription polymerase chain-reaction was used to quantify the relative levels of ftf, gtfB, gtfC, gtfD and vicR transcription of S. mutans in the presence of various dietary carbohydrates: sucrose, D-glucose, D-fructose, D-glucitol (D-sorbitol), D-mannitol and xylitol. Ftf was highly expressed at late exponential phase in the presence of sorbitol and mannitol. GtfB was highly expressed in the presence of all the above carbohydrates except for xylitol at early exponential growth phase and glucose and fructose at late exponential growth phase. Similar to gtfB, the expression of gtfC was also induced with the presence of all the tested carbohydrates except for xylitol at early growth and glucose and fructose at late exponential phase. In addition, no effect of mannitol on gtfC expression at early exponential phase was observed. GtfD was less influenced compared to the gtfB and gtfC, demonstrating enhanced expression especially in the presence of sorbitol, glucose, mannitol and xylitol at early exponential phase and mannitol at late exponential phase. VicR expression was induced only at the presence of xylitol at late exponential phase, and a decrease in expression was recorded at early exponential phase. Our findings show that dietary carbohydrates have a major influence on the transcription of ftf, gtfB, gtfC and gtfD, but less on vicR. Sorbitol and mannitol, which are considered as noncariogenic sugar substitutes, may indirectly affect caries by promoting biofilm formation via enhanced expression of gtfs and ftf. These results suggest regulatory circuits for exopolysaccharide gene expression in S. mutans.

Bacterial Proteins↗

PubMed1983

Inhibition of Streptococcus mutans by the lactoperoxidase antimicrobial system.

Inhibition of bacterial metabolism by the lactoperoxidase (LP)-hydrogen peroxide (H2O2)-thiocyanate system was studied with representatives of serotypes a through g of Streptococcus mutans. The aims were to determine whether the amount of H2O2 released from these catalase-negative bacteria is sufficient to activate the LP system and whether these oral bacteria are resistant to inhibition by the LP system, which is active in human saliva. When the washed, stationary-phase cells were incubated aerobically with LP, thiocyanate, and glucose (Glc), greater than 90% inhibition of Glc utilization and lactate production was obtained with strains that released large amounts of H2O2 (BHT, FA-1, OMZ-176); 20 to 50% inhibition was obtained with strains that released about half as much H2O2 (B-13, Ingbritt); and no inhibition was obtained with strains that released only small amounts of H2O2 (AHT, HS-6, GS-5, LM-7, OMZ-175, 6715-15). Inhibition was most effective at pH 5, whereas release of H2O2 and accumulation of the inhibitor (hypothiocyanite ion) were highest at pH 8. With H2O2-releasing cells from early stationary phase, preincubation with Glc abolished inhibition, though it did not influence H2O2 release. Cells harvested 24 h later were depleted of sulfhydryl compounds. Inhibition of these cells was abolished by preincubation with Glc and certain sulfhydryl or disulfide compounds (reduced or oxidized glutathione, cysteine or cystine). This preincubation increased cell sulfhydryl content but had no effect on H2O2 release. All strains were inhibited when incubated with LP, thiocyanate, and added (exogenous) H2O2. Smaller amounts of H2O2 were required to inhibit at pH 5, and larger amounts were required to inhibit cells preincubated with Glc or with Glc and the sulfhydryl or disulfide compounds. The results indicate that pH, amount of H2O2, cell sulfhydryl content, and stored-carbohydrate content determine susceptibility to inhibition.

Disulfides↗

PubMed1989

A human salivary protein which promotes adhesion of Streptococcus mutans serotype c strains to hydroxyapatite.

The aim of this study was to investigate the nature of one of the factors in human submandibular-sublingual (SMSL) saliva which promotes the adhesion of Streptococcus mutans serotype c strains to hydroxyapatite (HA) surfaces. Gel filtration chromatography of SMSL saliva on Trisacryl GF2000 gave a void volume peak which contained the major fraction of adhesion-promoting activity for S. mutans JBP to HA. Maximum adhesion-promoting activity, however, eluted slightly later than the maximum 220-nm absorbance of the void volume peak. Gel filtration of the void volume material after treatment with sodium dodecyl sulfate (SDS) gave an early-eluting larger peak followed by a smaller peak with which the adhesion-promoting activity was associated. SDS-polyacrylamide gel electrophoresis (SDS-PAGE) showed the presence of relatively slowly migrating material associated with the larger inactive peak, presumably mucin, and a faster-migrating band(s) associated with the smaller active peak. SDS-PAGE indicated molecular weights in the range of 300,000 to 350,000 by extrapolation from size standards. Comparison of SMSL from five individuals showed the presence of single bands or double bands associated with adhesion-promoting activity, indicating genetic polymorphism. The active material did not resemble either secretory immunoglobulin A, based on SDS-PAGE and immunoassay, or fibronectin, based on SDS-PAGE, and also differed in molecular weight from salivary mucins and salivary constituents previously reported to promote aggregation of certain oral bacteria, but a relationship to these materials cannot be excluded. This adhesion-promoting material may play a significant role in the initial colonization of tooth surfaces by S. mutans strains.

Bacterial Adhesion↗

PubMed2005

[Relationship of the genetic diversity within the V-region, P-region and C-terminus of surface protein of Streptococcus mutans to dental caries].

OBJECTIVE: To gain an understanding of the relationship between the genetic diversity within the V-region, P-region, C-terminus of surface protein of Streptococcus mutans (serotype c) and their adherent abilities. METHODS: The clinical isolates of S. mutans (serotype c) in two groups with different adherent abilities (cpm>2000, cpm<1000) had been prepared in our experimental laboratory. The genome DNA was extracted, and the spaP-pv (2060-3157 bp) and spaP-c (4003-4851 bp) were amplified by PCR, respectively. Genetic diversity was assessed by restriction fragment-length polymorphism (RFLP) with restriction endonucleases Alu I. RESULTS: (1) Two different patterns of spaP-pv RFLP among strains were revealed after the amplified product being digested with Alu I. The distributions of two genotypes (a and b) in the clinical strains with different adherent abilities differed significantly (P<0.05). The proportion of genotype b in the strains with higher adherent abilities was higher than that in the strains with lower adherent abilities. (2) Two different patterns (c and d) of spaP-c RFLP among strains were also revealed after the spaP-c being digested with Alu I. No statistically significant difference was observed in the distribution of the two genotypes in the clinical strains. CONCLUSION: The genetic diversity within spaP-pv of clinical isolates of S. mutans might be related to the differences of their adherent abilities.

Antigens, Surface↗

PubMed1979

Suppression of Streptococcus mutans in the mouths of humans by a dental prophylaxis and topically-applied iodine.

A prophylaxis followed by three topical applications of an iodine-potassium iodide solution significantly reduced the levels of Streptococcus mutans in fissure and approximal plaques and in saliva. Reductions persisted 20--24 weeks after treatment in salivary and approximal samples. A prophylaxis alone exerted a small and temporary reduction of S. mutans in occlusal fissure plaque, but did not reduce the levels of this organism in approximal plaque or in saliva. A significant relationship existed between the levels of S. mutans in saliva and the proportions of this organism in plaque. The dorsum of the tongue does not appear to constitute a significant reservoir for S. mutans following disinfecting procedures.

Administration, Topical↗

PubMed1991

Oral passive immunization against dental caries in rats by use of hen egg yolk antibodies specific for cell-associated glucosyltransferase of Streptococcus mutans.

The effect of polyclonal egg yolk immunoglobulin G antibodies (yIgG) raised against whole cells, cell-free (CF) glucosyltransferase (GTase), or cell-associated (CA) GTase of serotype c Streptococcus mutans was examined in terms of in vitro inhibition of virulence-related factors of S. mutans and protection of S. mutans-infected rats against the development of dental caries. Hens (18 weeks old) were immunized with formalin-treated whole cells, purified CF-GTase, or CA-GTase together with Freund's complete adjuvant. In addition, yIgG to surface protein antigen was used in some in vitro experiments for comparison with other antibodies. yIgG was purified by ammonium sulfate precipitation followed by DEAE-Sephacel column chromatography or fractional precipitation with ethanol. Purified yIgG was found to be a 220-kDa protein, which was dissociated into heavy and light chains upon addition of 2-mercaptoethanol. yIgG to whole cells and surface protein antigen gave a heavy aggregation of S. mutans organisms, while yIgG to CF- and CA-GTase specifically inhibited the enzymatic activity of the respective GTase. yIgG to CA-GTase and whole cells was found to clearly suppress the adherence of S. mutans cells to a glass surface. Specific-pathogen-free Sprague-Dawley rats that had been infected heavily and repeatedly with S. mutans and fed diet no. 2000 developed severe dental caries, while rats fed diet 2000 containing greater than or equal to 0.1% yIgG to CA-GTase showed a statistically significant reduction in dental plaque accumulation and caries development. Administration of yIgG to CF-GTase and whole cells failed to protect against caries. These results clearly suggest that yIgG to S. mutants CA-GTase specifically inhibited a virulence factor of this organism, i.e., insoluble glucan-synthesizing CA-GTase, resulting in a significant reduction in the development of dental caries.

Administration, Oral↗

PubMed1979

Quantitative structure-activity relationships for biguanides, carbamimidates, and bisbiguanides as inhibitors of Streptococcus mutans No. 6715.

Thirty-seven compounds, including 17 biguanides, 6 carbamimidates, and 14 bisbiguanides, were evaluated for potential antiplaque activity by measuring their minimum inhibitory concentrations [MIC (M)] against Streptococcus mutans no. 6715. Linear regression analysis was conducted with the log 1/MIC (M) values and log P, pi, sigma, and MR. The best correlation for the biguanides (r2 = 0.92) was obtained with log P and (log P)2. When the biguanides were included with the carbamimidates, essentially the same correlation (r2 = 0.91) was obtained with log P and (log P)2. The best correlation for the bisbiguanides (r2 = 0.70) was also obtained with log P and (log P)2. Use of an indicator variable (I) for the bisgiguanides allowed all three groups to be included in one equation, which accounted for over 87% of the variance in the data for inhibition of bacterial growth. These results from the classical parabolic model were also compared with those from the recently developed bilinear model.

Biguanides↗

PubMed1980

Prevalence of Streptococcus mutans serotypes, Actinomyces, and other bacteria in the plaque of children.

Selected microbial components in dental plaque were determined for children in Biddeford, Maine and Colombia, South America. Using cultural methods, Streptococcus mutans was detected in 51.4% of the Colombian children and 63.3% of the Maine children. Serotype c was predominant in both populations. The greatest difference between the two groups occurred with serotypes d and g which were present in 25% of the Colombian children with S. mutans and were not detected in the Maine children. In the specimens examined with specific FA conjugates. Actinomyces was the predominant genus, present in all individuals and comprising an average of 52% of all cells.

Actinomyces↗

PubMed2000

Extract of Juglandaceae regia inhibits growth, in-vitro adherence, acid production and aggregation of Streptococcus mutans.

Aqueous and alcoholic extracts from Juglandaceae regia, used as chewing sticks to maintain oral hygiene, were tested for their ability to inhibit the growth and some physiological functions of Streptococcus mutans. Both the aqueous and the alcoholic extract strongly inhibited the growth, in-vitro adherence, acid production and glucan-induced aggregation of S. mutans. At a concentration of 8% w/v, the aqueous extract produced a 95% inhibition (P < 0.05) of adherence of S. mutans to glass and a 40% inhibition (P < 0.05) of adherence to tooth surface. The alcoholic extract at a concentration of 10% w/v produced a 95% inhibition (P < 0.05) of adherence of S. mutans to glass and a 56% inhibition (P < 0.05) of adherence to tooth surface. At concentrations of 2% w/v the aqueous and alcoholic extracts significantly inhibited (P < 0.05) glucan-induced aggregation of S. mutans and the in-vitro salivary glycolytic reaction for up to 5 h. Bactericidal effects on S. mutans were also evident. At a concentration of 10% w/v, the zone of inhibition observed with the aqueous extract was 12+/-0.01 mm and that observed with the alcoholic extract was 12.6+/-0.02 mm. As the in-vitro studies had shown that both the aqueous and the alcoholic extract of J. regia, at concentrations of 10% w/v, could inhibit the growth as well as the acid-producing ability of S. mutans, they were tested at the same concentration for their activity in-vivo. Three subjects were employed. Parameters monitored were salivary bacterial count and salivary glycolysis. Mouth-rinsing with the aqueous but not the alcoholic extract significantly reduced total streptococcal counts in the salivary samples obtained up to, and including, 3 h after rinsing, compared with the counts obtained pre-rinsing or after placebo rinsing. Mouth-rinsing with the aqueous extract produced a 65%, 27% and 78% reduction (P < 0.05) in the streptococcal count in the salivary samples obtained 10 min, 1 h and 3 h after rinsing, respectively. Both the aqueous and the alcoholic extract also inhibited the glycolytic reaction by the salivary bacteria for up to 90 min post-rinsing. This study provides evidence to justify the use of J. regia sticks as an aid to maintain oral hygiene.

Acids↗

PubMed1980

Distribution of cross-reactive antigens A and B in Streptococcus mutans and other oral streptococci.

A collection of strains representing the various common species of oral streptococci was examined for the presence of antigens cross-reacting with A and B from Streptococcus mutans serotype c. Antigens cross-reacting with A were found only in S. mutans serotype b. Antigens cross-reacting with B were found in S. mutans serotypes a, c, d, e, f and g and also in strains of S. sanguis. All antigens cross-reacting with B were precipitated by antiserum to human heart tissue.

Antibodies, Bacterial↗

PubMed2000

Salivary mucin as related to oral Streptococcus mutans in elderly people.

MG1 (MUC5b and MUC4) and MG2 (MUC7), predominant mucins in human whole saliva, provide lubrication and antimicrobial protection for oral tissues. This study examines potential relationships between Streptococcus mutans titers in the oral cavity and the following: mucin concentrations; unstimulated and stimulated whole saliva flow rates; decayed, missing, and filled tooth surfaces; and age of 24 elderly patients. S. mutans titers were determined using Denticult SM. Mucin concentrations were determined using Stains-all, sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Logistic regression was used to identify potential relationships between the above variables. S. mutans classification served as the dependent variable. The remaining variables were possible predictor variables. The best model for predicting S. mutans category contained log MG2 as a predictor variable for all of its parameter estimates. No other set of parameter estimates were statistically significant. These results suggest that elevated S. mutans titers are significantly associated with diminished concentrations of MG2 in unstimulated whole saliva, as quantified in mucin-dye binding units.

Aged↗

PubMed2000

Construction and characterization of an effector strain of Streptococcus mutans for replacement therapy of dental caries.

An effector strain has been constructed for use in the replacement therapy of dental caries. Recombinant DNA methods were used to make the Streptococcus mutans supercolonizing strain, JH1140, lactate dehydrogenase deficient by deleting virtually all of the ldh open reading frame (ORF). To compensate for the resulting metabolic imbalance, a supplemental alcohol dehydrogenase activity was introduced by substituting the adhB ORF from Zymomonas mobilis in place of the deleted ldh ORF. The resulting clone, BCS3-L1, was found to produce no detectable lactic acid during growth on a variety of carbon sources, and it produced significantly less total acid due to its increased production of ethanol and acetoin. BCS3-L1 was significantly less cariogenic than JH1140 in both gnotobiotic- and conventional-rodent models. It colonized the teeth of conventional rats as well as JH1140 in both aggressive-displacement and preemptive-colonization models. No gross or microscopic abnormalities of major organs were associated with oral colonization of rats with BCS3-L1 for 6 months. Acid-producing revertants of BCS3-L1 were not observed in samples taken from infected animals (reversion frequency, <10(-3)) or by screening cultures grown in vitro, where no revertants were observed among 10(5) colonies examined on pH indicator medium. The reduced pathogenic potential of BCS3-L1, its strong colonization potential, and its genetic stability suggest that this strain is well suited to serve as an effector strain in the replacement therapy of dental caries in humans.

Animals↗

PubMed1984

Effect of cheese, with and without sucrose, on dental caries and recovery of Streptococcus mutans in rats.

The objective of this study was to determine the effect of aged and young cheddar cheese with and without added sucrose on dental caries and the associated recovery of implanted Streptococcus mutans. Very little caries was observed in rats consuming cheese without sucrose. There was an increase in caries in rats fed cheeses with 20% sucrose, but this increase was not significant. There was significantly greater caries activity in rats fed standard diets containing 20% or 5% sucrose (SLS or MIT 305) than in rats fed cheeses containing 20% sucrose. Rats fed cheese or powdered diets containing sucrose had significantly higher frequency of recovery and higher levels of S. mutans infection than did rats fed cheese containing no sucrose. This study confirms the low cariogenic potential and possible cariostatic activity of cheddar cheese in rats. Since cheddar cheese with sucrose did not significantly interfere with S. mutans implantation, the cariostatic mechanism is apparently unrelated to a direct antimicrobial effect on S. mutans.

Animals↗

PubMed1993

Protective salivary immunoglobulin A responses against Streptococcus mutans infection after intranasal immunization with S. mutans antigen I/II coupled to the B subunit of cholera toxin.

The B subunit of cholera toxin (CTB) has been shown to augment mucosal responses to microbial virulence antigens, including those of Streptococcus mutans, which is the principal etiologic agent of dental caries. In the present study, the surface fibrillar protein antigen of S. mutans, antigen I/II (Ag I/II), was chemically coupled to CTB (Ag I/II-CTB), and the conjugate was examined for its effectiveness in inducing salivary immune responses protective against S. mutans infection. Weanling Fischer rats were given Ag I/II-CTB (50 micrograms) by the intranasal route and then orally infected with a virulent strain of S. mutans. Gnotobiotic or conventional rats were given two or three additional immunizations, respectively, at about 2-week intervals. One week after each immunization, individual serum, saliva, and fecal samples were collected and stored frozen until assayed for antibody activity to Ag I/II and cholera toxin (CT) by an enzyme-linked immunosorbent assay. The rats were sacrificed 1 week after the last immunization, when mandibles were also collected from individual rats for assessment of S. mutans levels in plaque and caries activity. Rats immunized only or both immunized and infected showed a salivary immunoglobulin A (IgA) anti-Ag I/II response which reached significantly (P < 0.05) higher levels than those seen in nonimmunized, infected controls. A salivary IgA anti-Ag I/II response was also seen in rats infected only with S. mutans. Essentially no salivary antibody activity to CT was detected. Some serum anti-Ag I/II and anti-CT responses were seen in immunized animals. Serum IgG anti-Ag I/II responses were seen in immunized, infected rats and also in infected-only rats, suggesting that the responses were a result of infection with S. mutans. The immunized and infected rats had significantly (P < 0.05) lower levels of S. mutans in plaque and lower caries activity than nonimmunized, infected rats. These results indicated that intranasal immunization of rats with Ag I/II-CTB induced a protective salivary immune response which was associated with a reduction in S. mutans colonization and S. mutans-induced dental caries.

Animals↗

PubMed1978

Involvement of phosphoenolpyruvate in the catabolism of caries-conducive disaccharides by Streptococcus mutans: lactose transport.

The mechanisms for transport and hydrolysis of lactose were investigated in five cariogenic strains (HS6, AHT, FA1, NCTC 10449, and SL1) representing the four serogenetic groups of Streptococcus mutans. The systems for transport and hydrolysis of lactose had the characteristics of a phosphoenolpyruvate (PEP)-dependent lactose (Lac) phosphotransferase (PT) system and phospho-beta-galactosidase (P-beta-gal), respectively, in all strains tested, except strain HS6. Decryptified cells required PEP and Mg(2+) for transport of the non-metabolizable model beta-galactosides o-nitrophenyl-beta-d-galactopyranoside (ONPG) and thiomethyl-beta-d-galactopyranoside (TMG). Substitution of 2-phosphoglycerate (2-PG) for PEP also stimulated the Lac PT system. Other potential high-energy phosphate donors (adenosine tri-, di-, and monophosphates and guanosine triphosphate) did not stimulate the Lac PT system. Sodium fluoride had no effect upon the PEP-dependent Lac PT system in decryptified cells with PEP as the energy source; however, when 2-PG was used as the energy source, F(-) inhibited ONPG phosphorylation. With intact cells which must generate PEP endogenously, the presence of F(-) in concentration >/= 10 mM completely inhibited the Lac PT system, presumably through inhibition of 2-PG hydrolyase (EC 4.2.1.11; enolase). Both intact and decryptified cells accumulated a phosphorylated derivative of TMG that behaved chromatographically as TMG-phosphate. After alkaline phosphatase treatment, the derivative had an R(f) identical to that of TMG. No beta-galactosidase (beta-gal) activity was detected with ONPG as the substrate; hydrolysis occurred only when ONPG-6-phosphate was supplied as the substrate. Strain HS6 apparently transported lactose by an active transport-type system in which the accumulated intracellular product was the free disaccharide based on the following criteria: (i) ONPG transport and hydrolysis in decryptified cells was not stimulated by PEP; (ii) ONPG hydrolysis occurred in the absence of PEP; and (iii) ONPG-6-phosphate was not hydrolyzed. These data indicate that, in all strains tested except strain HS6, lactose transport was mediated by a PEP-dependent Lac PT system, resulting in accumulation of lactose-phosphate that was hydrolyzed by an enzyme similar to the P-beta-gal of group N streptococci and Staphylococcus aureus; conversely, strain HS6 transported and hydrolyzed lactose by a PEP-independent transport system and beta-gal, respectively.

Biological Transport↗

PubMed2006

Effects of Streptococcus mutans gtfC deficiency on mixed oral biofilms in vitro.

The aim of this study was to examine the influence of glucosyltransferase-gene-negative (gtf-) Streptococcus mutans strains unable to synthesize water-insoluble or soluble glucan on the structure and macromolecular diffusion properties of in vitro grown mixed oral biofilms. Biofilms modeling supragingival plaque consisted of Actinomyces naeslundii OMZ 745, Candida albicans OMZ 110, Fusobacterium nucleatum KP-F2, Streptococcus oralis SK 248, Veillonella dispar ATCC 17748T and one of the S. mutans strains UA159, OMZ 966, OMZ 937 or OMZ 977. Biofilms were grown anaerobically on sintered hydroxyapatite disks for 64.5 h at 37 degrees C. To perform confocal laser scanning microscopy analyses, microorganisms were stained with Syto 13 and extracellular polysaccharides (EPS) with Calcofluor. Macromolecular diffusion properties were measured following timed biofilm exposure to Texas-Red-labeled 70-kDa dextran. Results showed that replacing wild-type S. mutans by a gtfC- mutant led to an increase in the volume fraction occupied by cells from 29 to 48% and a decrease of the EPS volume fraction from 51 to 33%. No such changes were observed when the S. mutans wild-type strain was replaced by a gtfB- or gtfD- mutant. The diffusion coefficient of 70-kDa dextran in biofilms containing the gtfC- S. mutans was 16-fold higher than in biofilms with the wild-type strain indicating a strong macromolecular sieving effect of GTF C-generated glucans. Our data demonstrate the influence of EPS on the structure and macromolecular diffusion properties of an oral biofilm model and uncover our still limited knowledge of the function of EPS in biofilms and plaque.

Biofilms↗