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PubMed1986

Tight genetic linkage of a glucosyltransferase and dextranase of Streptococcus mutans GS-5.

A genetic library consisting of over 5000 clones with an average insert size of 6.9 kilobasepairs (kbp) of Streptococcus mutans GS-5 has been constructed in a bivalent plasmid vector pMK3, which is capable of replicating in Escherichia coli and Bacillus subtilis. The recombinant plasmid pSUCRI, containing a 6.0 kbp fragment of S. mutans GS-5 DNA, was the focus of this study. Using Southern hybridization, in vitro and in vivo gene expression techniques, and biochemical analysis, this clone was shown to encode the 55 kiloDalton (kDal) GS-5 gtfA gene product, as well as a 38 and a 66 kDal polypeptide. In addition to the gtfA gene, pSUCRI encodes a dextranase activity with specificity for alpha(1----6)-linked glucans, and with no detectable activity on mutan. The dextranase enzyme had an apparent molecular weight of 66 kDal as demonstrated by SDS-PAGE analysis of the proteins produced by a dextranase-negative deletion derivative. The pH optimum of the enzyme was approximately 6.0, and there was no detectable activity below pH 5.0. By subcloning various combinations of DNA fragments from pSUCRI, it was demonstrated that the dextranase gene (designated dexB) can be separated from the gtfA gene and still be efficiently expressed in both E. coli and B. subtilis. The dexB gene contained its own promoter and ribosome-binding site. The genetic linkage of the gtfA and dexB genes in the S. mutans GS-5 chromosome was confirmed by Southern hybridization and by the independent isolation of four distinct clones containing the gtfA gene and common flanking sequences. In addition to a glucosyltransferase and dextranase, an invertase-like activity is also encoded on pSUCRI, indicating that there is a cluster of genes on the S. mutans GS-5 chromosome which is devoted to the dissimilation of sucrose and concomitant synthesis or modification of glucans into a water-insoluble form, perhaps constituting an operon for glucan modification which can be coordinately regulated in response to environmental alterations.

Bacillus subtilis↗
PubMed1989

[Cariogenicity of Propionibacterium acnes, Streptococcus intermedius and Streptococcus mutans in germ-free rats].

A comparative study has been made on the cariogenic potentials of Propionibacterium acnes ATCC 11828, Streptococcus intermedius OE-1 and Streptococcus mutans OZ-1. The strains of P. acnes and S. intermedius have chondroitinase activity. As metabolic end-products, the P. acnes strain produces mainly a weak acid, propionic acid, whereas strong lactic acid is the main product of the strains of S. intermedius and S. mutans. Five germ-free rats were used for infection with each bacterial strain. The rats were fed with a 25% sucrose diet for 100 days and then sacrificed. The upper and lower molars were used for the determination of the smooth surface caries score. The right upper and lower jaws were used for the preparation of sections which were employed for the determination of the fissure caries score and microradiography. The left upper and lower jaws were decalcified and used for the preparation of thin sections for staining with Gram's, hematoxilin eosin, Mallory's, alcian blue-PAS, silver and toluidine blue stain. The results obtained were as follows: 1. The recoveries of infected cells in the specimens obtained by swabbing the oral cavities were in the order of 10(4) CFU/mg wet weight regardless of the strains injected. 2. Macroscopically, the P. acnes strain decalcified to a lesser extent some of the enamel surfaces of the lower molars. However, the S. intermedius strain produced mainly the fissure caries of the lower molars. The S. mutans strain destroyed the enamel extensively, resulting in the induction of rampant carious lesions. 3. The caries scores of smooth surface determined by Keyes's method were 19.4 +/- 7.8, 46.8 +/- 5.8 and 118.4 +/- 15.4 in the rats infected with the strains of P. acnes, S. intermedius and S. mutans, respectively. The fissure caries score determined by the modified König's method were 8.5, 22.3 and 36.5 in the sections prepared from the rats infected with the strains of P. acnes, S. intermedius and S. mutans, respectively. 4. Microradiography revealed no translucent area in the enamel and dentine of the P. acnes-infected molars, while in the S. intermedius-infected molars translucent areas were found at the dentino-enamel junction neighboring the bottoms of some fissures. The S. mutans-infected molars showed extensive translucent areas over the enamel and dentine of all of the molars. Even defects of the enamel and dentinal areas were observed in some of the molars. 5. The decalcified tooth sections were stained in a similar manner irrespective of the type of organisms used to infect them.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2006

Different roles of EIIABMan and EIIGlc in regulation of energy metabolism, biofilm development, and competence in Streptococcus mutans.

The phosphoenolpyruvate:sugar phosphotransferase system (PTS) is the major carbohydrate transport system in oral streptococci. The mannose-PTS of Streptococcus mutans, which transports mannose and glucose, is involved in carbon catabolite repression (CCR) and regulates the expression of known virulence genes. In this study, we investigated the role of EII(Glc) and EIIAB(Man) in sugar metabolism, gene regulation, biofilm formation, and competence. The results demonstrate that the inactivation of ptsG, encoding a putative EII(Glc), did not lead to major changes in sugar metabolism or affect the phenotypes of interest. However, the loss of EII(Glc) was shown to have a significant impact on the proteome and to affect the expression of a known virulence factor, fructan hydrolase (fruA). JAM1, a mutant strain lacking EIIAB(Man), had an impaired capacity to form biofilms in the presence of glucose and displayed a decreased ability to be transformed with exogenous DNA. Also, the lactose- and cellobiose-PTSs were positively and negatively regulated by EIIAB(Man), respectively. Microarrays were used to investigate the profound phenotypic changes displayed by JAM1, revealing that EIIAB(Man) of S. mutans has a key regulatory role in energy metabolism, possibly by sensing the energy levels of the cells or the carbohydrate availability and, in response, regulating the activity of transcription factors and carbohydrate transporters.

Biofilms↗
PubMedDate not supplied

IgA antibodies to Streptococcus mutans in caries-resistant and -susceptible children.

Previous studies have shown a positive correlation between salivary IgA antibody levels to Streptococcus mutans and caries resistance in adults. In this study, enzyme-linked immunosorbent assay (ELISA) was used to compare IgA antibody levels with S. mutans in whole and parotid saliva from 20 caries-susceptible (CS; DMFS > 5) and 20 caries-resistant (CR; DMFS < or = 1) children (aged 7-11 years). Whole salivary S. mutans numbers were significantly greater (P < or = 0.05) in the CS group (mean of 31.2% of total oral streptococci) than in the CR group (mean of 1.6% of total oral streptococci). Whole saliva, but not parotid saliva, from CR children had significantly higher (P < or = 0.05) levels of IgA antibodies to S. mutans than saliva from CS children. These results suggest that salivary IgA antibodies to S. mutans may play a role in natural protection from dental caries in children and that the source of increased salivary IgA antibody in CR children may be either the minor, submandibular, or sublingual salivary glands.

Antibodies, Bacterial↗
PubMed1995

Role of C-terminal direct repeating units of the Streptococcus mutans glucosyltransferase-S in glucan binding.

The C-terminal glucan-binding domain of the glucosyltransferase-S of Streptococcus mutans GS-5 contains five 65-amino-acid direct repeating units. A series of deletion derivatives of both the glucosyltransferase-S and its glucan-binding domain were constructed and analyzed. The results demonstrated that the four C-terminal direct repeating units constituted part of the minimum domain required for glucan binding.

Bacterial Adhesion↗
PubMed2001

Cloning of the Streptococcus mutans gene encoding glucan binding protein B and analysis of genetic diversity and protein production in clinical isolates.

Streptococcus mutans, the primary etiological agent of dental caries, produces several activities that promote its accumulation within the dental biofilm. These include glucosyltransferases, their glucan products, and proteins that bind glucan. At least three glucan binding proteins have been identified, and GbpB, the protein characterized in this study, appears to be novel. The gbpB gene was cloned and the predicted protein sequence contained several unusual features and shared extensive homology with a putative peptidoglycan hydrolase from group B streptococcus. Examination of gbpB genes from clinical isolates of S. mutans revealed that DNA polymorphisms, and hence amino acid changes, were limited to the central region of the gene, suggesting functional conservation within the amino and carboxy termini of the protein. The GbpB produced by clinical isolates and laboratory strains showed various distributions between cells and culture medium, and amounts of protein produced by individual strains correlated positively with their ability to grow as biofilms in an in vitro assay.

Amino Acid Sequence↗
PubMed2005

Passive immunization by lactobacilli expressing single-chain antibodies against Streptococcus mutans.

We compared the anticariogenic effect of lactobacilli expressing a single-chain antibody (scFv) against the SA I/II adhesin of Streptococcus mutans under the control of an inducible or a constitutive promoter. Both lactobacilli expressed equal amounts of scFv and agglutinated S. mutans bacteria expressing SA I/II to a similar level. In a rat caries model, transformed lactobacilli could be detected in the oral cavity throughout the duration of the study. Transformants containing the constitutive promoter were slightly more protective than those containing the inducible promoter suggesting that continuous in situ production of scFv in the oral cavity may be therapeutically superior to intermittent production.

Agglutination↗
PubMed2002

Streptococcus mutans biofilm formation: utilization of a gtfB promoter-green fluorescent protein (PgtfB::gfp) construct to monitor development.

The glucosyltransferases of Streptococcus mutans are recognized as important virulence factors for this cariogenic bacterium. To study the expression of the gtfB gene of S. mutans in biofilms, a gtfB promoter (PgtfB)-green fluorescent protein (GFP) reporter system was developed. A Streptococcus-Escherichia coli shuttle vector harbouring a PGTFB::gfp cassette was introduced into S. mutans GS-5, and the expression of GFP by the transformed S. mutans cells was confirmed by fluorescence microscopy. Furthermore, confocal laser scanning microscopy was carried out on biofilms attached to polystyrene plates; enhanced gtfB expression was observed in various microcolonies across these biofilms. To further test the hypothesis that gtfB expression is upregulated in biofilms, flow cytometry analysis was done on planktonic and biofilm cells; this analysis showed an approximately five-fold increase in gtfB expression in the biofilm cells relative to the planktonic cells. Real-time (TaqMan) PCR analysis confirmed that gtfB expression in the biofilm cells was enhanced relative to the planktonic cells. Previously, it has been suggested that the S. mutans gtfC gene might be co-transcribed with gtfB. Therefore, RT-PCR analysis was performed on gtfB-expressing S. mutans; this analysis demonstrated that gtfC was co-transcribed with gtfB. These results indicated that GFP expression can be utilized to examine gene regulation in S. mutans biofilm formation.

Biofilms↗
PubMed2003

Determination of mutacin activity and detection of mutA genes in Streptococcus mutans genotypes from caries-free and caries-active children.

Relationships between genetic diversity, mutacin production and sensitivity to mutacins in Streptococcus mutans were evaluated in 19 clinical isolates from caries-free and caries-active children. Mutacin production was tested against 30 indicator strains; results showed significant variations in the inhibitory spectra of the clinical isolates. There was no association between the inhibitory spectrum of the infecting strain and the caries experience or the level of mutans streptococci infection of the host. Homology to the mutA gene coding for mutacin II was detected in one clinical isolate; none of the clinical isolates showed homology to the mutA genes coding for mutacins I or III. Genotyping by random amplified polymorphic DNA (RAPD) reactions grouped the isolates into three clusters, but no correlation was found between any of the clusters and mutacin activity, caries experience or level of mutans streptococci in the host.

Bacteriocins↗
PubMed1985

Addition of xylitol to the growth medium of Streptococcus mutans OMZ 176--effect on the synthesis of extractable glycerol-phosphate polymers.

Addition of 5% xylitol to growing cultures of Streptococcus mutans OMZ 176 reduced the amount of extractable glycerol-phosphate polymers in these cells compared to S. mutans cultures grown in medium with 5% glucose added. The glycerol-phosphate polymers were extracted from the cells by hot phenol-water-extraction, and separated by column chromatography. Lipoteichoic acid (LTA) was identified by indirect haemagglutination tests and lipid analysis. The amount of LTA extracted from the cells or present in the medium was not significantly different. It is suggested that the accumulation of intracellular xylitol-phosphate observed in a previous study causes an effect similar to glucose starvation, which is known to affect the composition of the cell wall.

Dental Plaque↗
PubMed1992

Molecular genetic analysis of the catalytic site of Streptococcus mutans glucosyltransferases.

In the present communication molecular genetic approaches have been utilized to confirm the nature of the catalytic site of Streptococcus mutans glucosyltransferases (GTF)s. Site-directed mutagenesis was used to convert the putative sucrose binding Asp-451 of the GTF-I enzyme from S. mutans GS5 to Glu, Asn, and Thr. All three of the resulting mutated enzymes displayed no detectable sucrase or GTF activities. By contrast, mutation of nearby Asp residues did not markedly reduce enzymatic activity. The inactive enzymes also appear to bind acceptor dextrans as well as the parental enzyme. These results confirm the essential role of Asp-451 of the GTF-I from strain GS5 and analogous Asp residues in other related GTFs in enzymatic activity.

Amino Acid Sequence↗
PubMed2004

Role of peptide antigen for induction of inhibitory antibodies to Streptococcus mutans in human oral cavity.

The alanine-rich repeating region (A-region) in the surface protein antigen (PAc) of Streptococcus mutans has received much attention as an antigenic component for vaccines against dental caries. The PAc (residue 361-386) peptide in the A-region possesses a multiple binding motif (L- -V-K- -A) to various HLA-DR molecules and a B-cell core epitope (- Y- - -L- -Y- - - -) that recognizes the inhibiting antibody to S. mutans. In the present study, we investigated the immunogenicity of the PAc (361-386) peptide in humans and regulators of induction of the anti-PAc (361-386) peptide IgA antibody (aPPA) in saliva. The PAc (361-386) peptide was confirmed as an ideal peptide antigen for induction of the inhibiting antibody to S. mutans in 151 healthy human subjects (36.6 +/- 12.6 years old) by quantitative analyses of oral bacteria and ELISA, as the aPPA titre in human saliva decreased significantly in an age-dependent manner. Homozygous DRB1*0405 and 1502, and heterozygous DRB1*0405/1502 showed a negative association with production of aPPA and tended to reduce the number of total streptococci in saliva. In contrast, the DRB1*1501 allele was significantly correlated with a high level of induction of the antibodies, and also tended to reduce lactobacilli and mutans streptococci. Further, peptide immunogenicity was confirmed in NOD-SCID mice grafted with human peripheral blood mononuclear cells. Our results indicate that the interplay between regulators such as age, DRB1 genotype, cytokines, and peptide immunogenicity may provide a potential means for developing a vaccine useful for the prevention of dental caries as well as their diagnosis.

Adult↗
PubMed2000

Construction of region-specific partial duplication mutants (merodiploid mutants) to identify the regulatory gene for the glucan-binding protein C gene in vivo in Streptococcus mutans.

The gbpC gene encoding the glucan-binding protein C which is involved in dextran (glucan)-dependent aggregation (ddag) of Streptococcus mutans has been identified by random mutagenesis. We analyzed ddag(-) mutants containing the intact gbpC gene and found that these mutants possessed a large and characteristic duplication of a region of the chromosome which was responsible for the phenotype. Based upon characterization of these duplications, we developed a strategy to introduce a duplication into any specific region of the chromosome of these organisms. The 690-bp gene responsible for the ddag(-) phenotype was identified within a 60-kb region by observing ddag (positive or negative) phenotypes of successively constructed specific duplication mutants.

Bacterial Proteins↗
PubMed1987

Pulp response to Streptococcus mutans.

The maxillary molar pulps of germ-free rats were mechanically exposed, and suspensions of a strain of freshly grown Streptococcus mutans were applied to the pulp wounds. The pulps were left open to the oral environment, and the animals were maintained in the isolator until they were killed in groups after 2, 7, and 28 days. After 2 days there was little evidence of any pulp response. In the 7-day group early pulp necrosis was present. No evidence of inflammatory infiltration was detected in either the 2- or 7-day animals. After 28 days there was extensive pulp necrosis in many specimens. Dentine bridges were present in fewer than one fourth of the teeth.

Animals↗
PubMed1991

Effects of anaerobiosis and aerobiosis on interactions of human polymorphonuclear leukocytes with the dental plaque bacteria Streptococcus mutans, Capnocytophaga ochracea, and Bacteroides gingivalis.

Human polymorphonuclear leukocytes (PMN) were able to generate and release superoxide anions upon stimulation of Streptococcus mutans, Bacteroides gingivalis, and Capnocytophaga ochracea when incubated aerobically but not when incubated anaerobically. Lysozyme release and phagocytosis by PMN were independent of oxygen, and no difference between PMN incubated aerobically or anaerobically was observed (PMN stimulated by B. gingivalis released 7.6% total lysozyme when aerobic and 6.9% when anaerobic). There were variations in lysozyme release and phagocytosis for the three organisms, particularly for phagocytosis. B. gingivalis and C. ochracea yielded lower phagocytosis values than those for S. mutans, e.g., at 1 h 67% of the initial inoculum of S. mutans was phagocytosed (versus only 40% for B. gingivalis). Transmission electron microscopy showed that both S. mutans and B. gingivalis were internalized into classical phagolysosomes. In contrast, C. ochracea showed two forms of internalization; C. ochracea either formed a classical phagolysosome or was tightly bound in the cytoplasm with no surrounding cell membrane. Intracellular killing of S. mutans and C. ochracea was unaffected by anaerobiosis, but killing of C. ochracea was much lower than that of S. mutans (1 x 10(7) to 2 x 10(7) bacteria killed compared with 5.1 x 10(7) bacteria killed at 6 h). In contrast, a greater number of B. gingivalis was killed in the presence of oxygen (5.3 x 10(7) bacteria were killed when aerobically incubated and 1.9 x 10(7) bacteria were killed when anaerobically incubated). These results suggest that the ability to survive anaerobically may enable some bacteria to evade PMN killing; however, abnormal phagocytosis may represent a more efficient way to evade both oxygen-dependent and -independent killing mechanisms, leading to enhanced virulence of the organism.

Aerobiosis↗
PubMed1997

Transcriptional analysis of the Streptococcus mutans hrcA, grpE and dnaK genes and regulation of expression in response to heat shock and environmental acidification.

The dental pathogen Streptococcus mutans persists and causes diseases in highly dynamic environments and gains a selective ecological advantage in environmental conditions that frequently exceed the limits for growth of the organism, particularly with regard to environmental pH. The goal of this study was to begin a molecular genetic analysis of a major stress protein, DnaK/Hsp70, to begin to understand how stress responses are regulated in this lactic acid bacterium and to establish a relationship between dnaK gene expression and exposure to acidic environments. Cloning and nucleotide sequence analysis revealed that the dnaK gene is preceded by, and is in an operon-like arrangement with, the hrcA and grpE genes, although intergenic spacing was unlike that described in other bacteria. An inverted repeat (a CIRCE element) was identified by sequence analysis and, using primer extensions, a heat shock-responsive, sigmaA-type promoter, P1, 5' to the hrcA gene, and a sigmaB-type promoter, 5' to the grpE translational start site, were identified. No promoters were detected between grpE and dnaK. A strain carrying a strongly polar insertion in the hrcA gene had markedly diminished levels of dnaK mRNA, indicating that dnaK was transcribed as part of an operon from P1, and to a lesser extent from P2. Results from physiological manipulation of S. mutans in continuous chemostat culture demonstrated that steadystate levels of S. mutans dnaK mRNA and DnaK protein were (i) increased in response to acid shock; (ii) elevated in acid 'adapted' cells; and (iii) induced in response to alkali shock of acid 'adapted' cells. In all cases, increased amounts of dnaK mRNA could be correlated with enhanced transcription from P1. This study provides the first detailed analysis of the expression of a heat shock gene from an oral isolate, and the evidence provided suggests that sigmaB-like promoters may also be involved in class I heat shock gene expression in some Gram-positive organisms.

Amino Acid Sequence↗
PubMed1989

Adsorbed salivary acidic proline-rich proteins contribute to the adhesion of Streptococcus mutans JBP to apatitic surfaces.

Experimental pellicles formed on hydroxyapatite (HA) beads from parotid or submandibular saliva promoted the adhesion of Streptococcus mutans JBP cells to a greater extent than did pellicles prepared from buffer, human plasma, or serum. The nature of the salivary components responsible was studied by the preparation of pellicles from fractions of parotid saliva obtained by chromatography on Trisacryl GF 2000 columns. Two groups of fractions promoted attachment of the organism. Components migrating in the high-molecular-weight mucin fraction were most effective, but a later-eluting fraction also possessed adhesion-promoting activity. Subfractionation of the latter material indicated that the adhesion-promoting activity was associated with the acidic proline-rich proteins (PRPs). Pellicles prepared from 10-20-micrograms/mL solutions of pure PRP-1 were effective in promoting attachment of S. mutans JBP cells. PRP-3 was less effective, while human salivary statherin, fibrinogen, fibronectin, type 1 collagen, and the amino-terminal tryptic peptide derived from PRP-1 were ineffective. The quantities of 150-residue and 106-residue PRPs and of statherin, which became incorporated into experimental pellicles prepared from saliva, were estimated with use of radiolabeled protein tracers. The data obtained suggest that these proteins compete for similar binding sites on HA, and that their ratios in saliva would therefore influence the quantity of the larger PRPs that become incorporated into the pellicle. Such competition may contribute to the variability observed in the adhesion-promoting activities of different saliva samples.

Adsorption↗