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PubMed1989

Inhibition by maltose, isomaltose, and nigerose of the synthesis of high-molecular-weight D-glucans by the D-glucosyltransferases of Streptococcus sobrinus.

Two D-glucosyltransferases are produced by Streptococcus sobrinus C211. One (GTF-S) catalyzes the conversion of sucrose into soluble alpha-(1----6)-linked alpha-(1----3)-branched D-glucans, and the other (GTF-I), of sucrose into alpha-(1----3)-linked alpha-(1----6)-branched D-glucans. These enzymes were studied by using maltose, isomaltose, and nigerose as inhibitors. Maltose and isomaltose were found to be competitive inhibitors of GTF-S, whereas nigerose has no effect on GTF-S activity. The Ki values for maltose and isomaltose were determined to be 11 and 15mM, respectively. Maltose, isomaltose, and nigerose competitively inhibit GTF-I. The Ki values for these inhibitors were found to be approximately 0.8, 2.5, and 15mM, respectively. The inhibitory properties of each disaccharide are interpreted in terms of conformational comparisons with sucrose.

Carbohydrate Conformation↗

PubMed1990

Characterization of cross-reactive polysaccharide antigen with serotype a and d strains from Streptococcus sobrinus 6715.

The polysaccharide antigen (designated SI) from Streptococcus sobrinus 6715 (serotype g) which cross-reacts with serotype a and d strains was purified by a specific anti-cross-reactive g-a antibody-Sepharose 4B affinity column. By a double immunodiffusion analysis, the SI antigen was found to lack the serotype-specific g site, but contained the cross-reactive sites g-a, g-d and g-(a-d) on a single molecule. Polysaccharide SI was composed of galactose, glucose and rhamnose in a molar ratio of 4.79:1.52:1. The results of the test on the inhibition of the precipitin reaction and methylation analysis suggested that the cross-reactive site g-a of the SI antigen appeared to have two regions, one containing galactose residues and the other, beta-linked glucose residues.

Antigens, Bacterial↗

PubMedDate not supplied

Detection of Streptococcus mutans and Streptococcus sobrinus on the permanent first molars of the Mosuo people in China.

Streptococcus mutans and Streptococcus sobrinus are associated with the development of dental caries. The purpose of this study was to differentiate these bacteria by morphology, biochemical characteristics and PCR, and to compare their occurrence with the prevalence of dental caries in the Mosuo people. Plaque samples were collected from the permanent first molar in 126 Mosuo people (83 females, 43 males, aged 25-55 years, average age 36.1 +/- 7.73). Dental status was recorded as DMFT by WHO caries diagnostic criteria. Males had a significantly lower prevalence of caries and DMFT than females: 11.4 vs. 86.9% and 1.65 vs. 6.95, respectively (p<0.001). Morphological and biochemical tests gave unreliable results. The prevalence of S. mutans and S. sobrinus was 75.4 and 57.1%, respectively. 26.5% of females and 53.5% of males were positive for S. mutans alone, 18.1% of females and 16.3% of males were positive for S. sobrinus alone, while 50.6% of females and 18.6% of males were positive for both S. mutans and S. sobrinus and 4.8% of females and 11.6% of males were negative for both species. The DMFT scores of subjects positive for both S. mutans and S. sobrinus were significantly higher than of those positive for either S. mutans or S. sobrinus alone. These results indicate that subjects harboring both S. mutans and S. sobrinus have a significantly higher prevalence of dental caries than those with S. mutans or S. sobrinus alone.

Adult↗

PubMed2002

Cloning and nucleotide sequence analysis of the Streptococcus sobrinus gtfU gene that produces a highly branched water-soluble glucan.

Streptococcus sobrinus has four gtf genes, gtfI, gtfS, gtfT, and gtfU, on the chromosome. These genes correspond respectively to the enzymes GTF-I, GTF-S1, GTF-S2, and GTF-S3. An Escherichia coli MD66 clone that contained the S. sobrinus gtfU gene was characterized. Immunological properties showed that the protein produced by the E. coli MD66 clone was similar to S. sobrinus GTF-S1. Biological properties and a linkage analysis of the glucans by 13C NMR spectrometry revealed that the protein produced by the E. coli MD66 clone was GTF-S1.

Amino Acid Sequence↗

PubMed1991

Antimicrobial susceptibility of 1042 strains of Streptococcus mutans and Streptococcus sobrinus: comparison from 1985 to 1989.

A total of 1042 strains of Streptococcus mutans and Streptococcus sobrinus isolated between 1985 and 1989 were tested to study the evolution of their sensitivity to penicillin, amoxycillin, amoxycillin/clavulanic acid, cefuroxime, tetracycline, erythromycin, spiramycin, acetyl spiramycin, lincomycin and clindamycin. The strains were taken from stock cultures and isolated from human saliva and dental plaque. The minimal inhibitory concentration (MIC) was determined by an agar dilution method. Except for spiramycin and acetyl spiramycin, all the antibiotics inhibited 100% of the strains with concentrations less than or equal to 2 micrograms/ml. Microorganisms from both species underwent a slow progressive loss of sensitivity to all the antibiotics over a 5-year period of study, showing statistically significant results in most cases.

Dental Plaque↗

PubMed1992

An 87-kilodalton glucan-binding protein of Streptococcus sobrinus B13.

An 87-kDa glucan-binding protein (GBP) of Streptococcus sobrinus B13 (serotype d) was isolated and purified from extracellular culture supernatant by using affinity chromatography on Sephadex G-50 and elution with a guanidine HCl gradient. Western blot (immunoblot) analysis showed it to be antigenically related, but not completely identical, to the 74-kDa GBP of Streptococcus mutans Ingbritt. The 87-kDa GBP has no glucosyltransferase activity. A possible role for this GBP in the cariogenicity of S. sobrinus B13 is suggested.

Carrier Proteins↗

PubMed1988

Suppression of Streptococcus sobrinus 6715 (g) in plaques by Streptococcus mutans 32K (c).

The dental plaque of 96 healthy donors was screened for the production of such antibacterial substances as mutalipocin and bacteriocin and 192 strains of mutans streptococci isolated: 28 produced mutalipocin and 22 produced bacteriocin. Mutalipocin produced by these 28 S. mutans strains possessed similar biochemical and biological characteristics of well-characterized mutalipocin-producing strain S. mutans 32K (serotype c). When equal amounts of S. mutans 32K and S. sobrinus 6715 (g) were cultured together, cells of S. sobrinus 6715 were completely killed in 18 h. In addition, S. mutans 32K inhibited in vitro plaque formation by S. sobrinus 6715, and S. mutans 32K also eliminated in vitro plaque preformed by S. sobrinus 6715. In rat experiments, S. mutans 32K could pre-emptively colonize in plaque preformed by S. sobrinus 6715. On the other hand, S. sobrinus 6715 could not colonize in plaque preformed by S. mutans 32K. The results indicate that S. mutans serotype c which produces antibacterial substances is able to invade dental plaque and replace the other mutans streptococci. This investigation offers one of the possible explanation why S. mutans serotype c is a predominant species among mutans streptococci in human plaque.

Animals↗

PubMed1995

Purification, characterization, and specificity of dextranase inhibitor (Dei) expressed from Streptococcus sobrinus UAB108 gene cloned in Escherichia coli.

The dextranase inhibitor gene (dei) from Streptococcus sobrinus UAB108 was previously cloned, expressed, and sequenced. Its gene product (Dei) has now been purified as a single band with apparent molecular mass of 43 kDa, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The specific activity of Dei increased 121-fold upon purification. Most Dei activity (91.2%) was located in the periplasmic fraction from recombinant Escherichia coli cells. Dei competitively inhibits dextranase (Dex). This competitive inhibition mechanism has been further shown by detection and recovery of the intermediate enzyme-inhibitor (Dex-Dei) complex by gel filtration technology using fast protein liquid chromatography. Calibration of their molecular masses indicated that native Dei exists as a tetramer, Dex exists as dimer, and the Dex-Dei complex consists of two Dex molecules with two Dei molecules. Deletion analysis indicates that the intact Dei molecule is essential for Dei activity but not for glucan binding and immune cross-reaction. Dei is a special kind of glucan-binding protein with ability to inhibit Dex with high specificity. It can inhibit endogenous Dex, which can make more branches in glucan with the cooperation of the glucosyltransferase GTF-I. This inhibition cause the accumulation of water-soluble glucan. The latter reaction product can inhibit plaque formation and adherence of the mutans group of streptococcal cells. Dei derived from S. sobrinus UAB108 can inhibit only Dex from S. sobrinus (serotypes d and g), S. downei (previously S. sobrinus, serotype h), and S. macacae (serotype h). This finding suggests that Dei is another important protein existing in some serotypes of the mutans group of streptococci which participates in sucrose metabolism through its interaction with Dex.

Bacterial Proteins↗

PubMed2001

Differentiation of Streptococcus mutans and Streptococcus sobrinus via genotypic and phenotypic profiles from three different populations.

Routine identification of Streptococcus mutans and Streptococcus sobrinus is generally based upon growth on various selective media, colony morphology and biochemical characteristics. We examined various approaches of differentiating these two species through a combination of the conventional phenotypic methodology with chromosomal DNA fingerprint (CDF) and arbitrarily primed polymerase chain reaction (AP-PCR) methods. Initially, ten ATCC type strains and 20 randomly selected clinical isolates of mutans streptococci (MS) were characterized and grouped into two major types based on patterns generated by the CDF using HaeIII digestion. The CDF's patterns with restriction fragments equal to or greater than 6.6 kb were defined as the CDF-1 group. The CDF's patterns with restriction fragments less than 6.6 kb were defined as the CDF-2 group. Both groups were then examined for biotype, serotype, and composition of DNA via thermal denaturation. AP-PCR was applied and evaluated for the capability of delineating S. mutans from S. sobrinus strains. Results of this study showed that all CDF-1 strains fit within a G+C range of 36.2% to 42.2%, whereas the CDF-2 strains had a G+C range of 45.8% to 47.0%. The serotyping assay exhibited 100% sensitivity, 90% specificity and 86.7% agreement with the CDF. The biotyping assay presented the poorest specificity (38.5%), indicating the highest variability. The capability of AP-PCR in differentiation of S. mutans from S. sobrinus was comparable to the CDF method, suggesting that either of these two approaches can and may serve as a viable alternative method to serotyping or biotyping of MS.

Analysis of Variance↗

PubMed1995

Subinhibitory concentrations of antibiotics affect cell surface properties of Streptococcus sobrinus.

Several antibiotics, at subinhibitory concentrations, caused an increase in the ability of Streptococcus sobrinus to bind alpha-1,6-glucans, whereas other antibiotics decreased glucan binding. In every case, glucan binding was inversely proportional to cell surface hydrophobicity. High levels of glucan-binding activity resulted in low levels of hydrophobicity, whereas low levels of glucan binding caused high levels of cellular hydrophobicity. The results show that low concentrations of antibiotics may modulate lectin and hydrophobin adhesins in streptococci.

Alkanes↗

PubMed1995

Effect of polyclonal and monoclonal antibodies on surface properties of Streptococcus sobrinus.

In this study, the effect of antibody adsorption on physicochemical properties of Streptococcus sobrinus was studied. Bacteria were preincubated with polyclonal antibodies or with OMVU10, a monoclonal antibody (MAb) reactive with S. sobrinus. The zeta potentials and the hydrophobicity as determined by microbial adhesion to hydrocarbons were measured in potassium phosphate buffer with a pH ranging from 2 to 9. S. sobrinus preincubated with polyclonal antibodies was positively charged at pH 2, 3, and 4 and had an isoelectric point at pH 4.8. Untreated S. sobrinus cells or cells preincubated with MAbs were negatively charged over the whole pH range. X-ray photoelectron spectroscopy showed a decrease in O/C and P/C ratios for bacteria preincubated with polyclonal antibodies. A combination of the pH-dependent zeta potential and the X-ray photoelectron spectroscopy data of the overall chemical composition of the cell surface suggests that polyclonal antibody adsorption occurs through blocking of surface phosphate. The measurement of hydrophobicity by microbial adhesion to hydrocarbons revealed that S. sobrinus preincubated with polyclonal antibodies was hydrophobic (90% of the bacteria bound to hexadecane), whereas the controls were relatively hydrophilic. S. sobrinus preincubated with OMVU10 was found to be more hydrophobic than the controls at pH 5 and 7. Hydrophobicity as measured by water contact angles showed an increase in hydrophobicity when S. sobrinus was preincubated with polyclonal antibodies. The epitopes to which the antibodies are directed were visualized by immunogold labeling and electron microscopy. The results suggested that OMVU10 is reactive with only a few epitopes of the cell surface, whereas polyclonal antibodies were found to be reactive with many epitopes. In conclusion, adsorption of polyclonal antibodies was found to influence the overall physicochemical surface properties of the organism, probably by forming a coating over the whole cell surface. Adsorption of MAbs was more localized, which could explain their lesser influence on these surface properties.

Adsorption↗

PubMed1993

Four different types of glucans synthesised by glucosyltransferases from Streptococcus sobrinus.

Four different kinds of glucosyltransferases (GTFs) were purified from the cariogenic bacterium Streptococcus sobrinus AHT. One of them (GTFP3) produced water-insoluble glucan with the alpha-1,3 linkage, exclusively. The others (GTFP1, P2 and P4) produced water-soluble glucans. GTFP2 produced oligosaccharides with linear 1,6-alpha-D-glucan structure. Since GTFP1 and P4 produce similar molecular weight glucans, the structural differences between these glucans remain unclear. To clarify the difference between GTFP1 and P4 products, the glucan structures were investigated by methylation analysis with gas liquid chromatography and gas liquid chromatography-mass spectrometry. The glucan synthesised by GTFP1 was 1,6-alpha-D-glucan with a high percentage (25.9 mol%) of 1,3-alpha-D-linked units. The other glucan synthesised by GTFP4 contained 1,6-alpha-D-glucan with 1,3,6-alpha-D-glucose (18.5 mol%).

Glucans↗

PubMed1997

Purification, and biochemical and biological characterization of an immunosuppressive and lymphocyte mitogenic protein secreted by Streptococcus sobrinus.

An immunosuppressive/mitogenic (ISM) protein was purified from the supernatants of cultures of Streptococcus sobrinus with an isoelectric point of 4.75 and a relative molecular mass of 38 kDa (p38). Treatment of C57BL/6 mice with p38 induced an increase in the numbers of non-specific splenic Ig-secreting plaque-forming cells (PFC) with peak responses on day 3 for IgM-secreting PFC and on day 5 for IgG-secreting PFC, with an isotype pattern consisting predominantly of IgG2a and IgG2b. This increase was accompanied by a lymphocyte blastogenic response of both T and B lymphocytes. The in vitro effects of p38 on pure B, T and total splenic lymphocytes indicated that this ISM protein was primarily a B cell mitogen, being T cells activated subsequently by the generation of B blasts. Suppression of the murine primary immune response against sheep red blood cells was observed in C57BL/6 mice treated 4 days before with p38. The amino acid sequence of the N-terminus of p38 has a significant similarity with several enolases, particularly with rabbit enolase. However, the biological effects ascribed to p38 have not been detected after in vivo treatment with that enolase. The immunosuppressive effect of p38 was abrogated by depletion of IL-10 but not of IL-4. In agreement with this observation IL-10 was the only cytokine detected in serum of C57BL/6 mice after p38 treatment and the peak of serum levels was observed as soon as 2 h after treatment.

Amino Acid Sequence↗

PubMed1998

Structural and antigenic characteristics of Streptococcus sobrinus glucan binding proteins.

Three purified glucan binding proteins (GBP-2, GBP-3, and GBP-5) from Streptococcus sobrinus 6715 were compared structurally by mass spectroscopy of tryptic fragments and antigenically by Western blot analysis with rat antisera to each GBP or to peptides containing putative glucan binding epitopes of mutans streptococcal glucosyltransferases. Structural and antigenic analyses indicated that GBP-3 and GBP-5 are very similar but that both are essentially unrelated to GBP-2. None of these S. sobrinus GBPs appeared to have a strong antigenic relationship with GBPs from Streptococcus mutans. Thus, S. sobrinus GBP-2 and GBP-3 appear to be distinct proteins with potentially different functions. S. sobrinus GBP-5 may be a proteolytic fragment of GBP-3, or, alternatively, the genes coding for these proteins may be closely related.

Amino Acid Sequence↗

PubMed1983

Dextran-induced aggregation in a mutant of Streptococcus sobrinus 6715-13.

A mutant of wild-type Streptococcus sobrinus 6715-13 has been isolated which resists aggregation by exogenous dextran. This variant is able to form adherent plaque deposits in vitro when cultured in the presence of sucrose and has dextranase activity. In these respects it is the complement of previously described isolates which are plaque formation defective but aggregation normal. Measurements of the incorporation of glucose from glucosyl-labeled sucrose into glucan by cell-associated glucosyltransferase enzyme activity and the thermal labilities of catalytic and receptor functions, as well as the binding of labeled dextrans to the cells, provide evidence that neither dextranase nor glucosyltransferase is the receptor involved in dextran-induced aggregation. Blockage of such bacterial aggregation by anti-glucosyltransferase or anti-dextranase sera suggests cross-reactivity between the antigenic determinants of proteins which recognize alpha(1-6) glucan linkages. A model is proposed, consistent with these and previous findings, in which enzymatic function precedes dextran receptor activity in emergence from the cell. It is also proposed that dextran receptor components of the multireactive glucosyltransferase enzyme(s) and dextranase(s) are spatially separate from, although functionally and antigenically related to, the receptors on the bacterial surface involved in dextran-induced aggregation.

Agglutination↗

PubMed1992

On the mechanism of xylitol-dependent inhibition of glycolysis in Streptococcus sobrinus OMZ 176.

1. The mechanism of xylitol-dependent inhibition of glycolysis in Streptococcus sobrinus OMZ 176 was investigated in aerobically and anaerobically grown cells. 2. Glucose-stimulated glycolysis was followed polarographically, by radio-HPLC-analyses of glycolytic intermediates, by measurement of ATP generated, and spectrophotometric monitoring of extent of NAD(P)+/NADPH-status. 3. Xylitol added to suspensions of S. sobrinus inhibited O2 uptake by approximately 20%, and led to a corresponding decrease in rate of lactate formation in aerobic and anaerobic cells. 4. Xylitol also delayed the onset of the glucose-dependent rapid reduction of NAD(P)+ by approximately 1 min, although the total extent of reduction was not significantly affected compared to control cells. 5. The inhibitory effect of xylitol on glucose dependent ATP synthesis, however, was decreased by 70-80%. 6. Hence the dramatic decrease in glucose-dependent synthesis of ATP may be the direct cause of decreased bacterial growth in the presence of xylitol. 7. A mechanism explaining the observed phenomena is proposed.

Adenosine Triphosphate↗

PubMed1993

Essential amino acids involved in glucan-dependent aggregation of Streptococcus sobrinus.

The active site of the glucan-binding lectin (or agglutinin) (GBL) of Streptococcus sobrinus was probed by specific amino acid modifying reagents. Reagents specific for carboxylates, imidazolium, phenolic, and lysyl residues inactivated the cell bound GBL, whereas agents specific for sulfhydryl, disulfide, and guanidinium groups had no effect on the lectin. A low molecular weight alpha-(1-->6)-glucan provided partial protection against the reagents which inactivated the protein, whereas an alpha-(1-->4)-glucan, incapable of complexing with the lectin, afforded no protection. A reagent specific for tryptophan, 2-hydroxy-5-nitrobenzyl bromide (HNB) did not cause a loss of GBL activity, although N-bromosuccinimide, a reagent capable of oxidizing tryptophan and less selective than HNB, was a very effective inhibitor of the glucan-dependent cellular aggregation. In the latter case, alpha-(1-->6)-glucan did not protect. Hydroxylamine partially restored the loss of lectin activity due to treatment of the cells with N-acetylimidazole (highly specific for tyrosine), glycine methyl ester plus water-soluble carbodiimide (specific for carboxylates), and diethylpyrocarbonate (specific for histidine). Because the soluble form of GBL rapidly loses activity when purified, it was necessary to perform the chemical modification of the amino acid side chains employing the cell-bound form of the lectin. Because specific ligand [alpha-(1-->6)-glucan] protected against the inactivation of the agglutinin by selected reagents and because lectin activity could be restored in some cases, it was possible to identify likely essential amino acid residues needed for glucan binding. The results, taken together, suggest that aspartic (and/or glutamic) acid, histidine, lysine, and tyrosine are critical amino acids responsible for agglutinin activity. Present efforts are directed to the design and synthesis of glucan analogues which may serve as affinity inactivating agents of the lectin. Such glucan derivatives may be of value in studies on the role of the lectin in cariogenesis.

Amino Acids↗

PubMed1993

Nucleotide sequence analysis of the gtfT gene from Streptococcus sobrinus OMZ176.

The gtfT gene and its upstream region isolated from the Streptococcus sobrinus OMZ176 chromosomal DNA were sequenced. The gtfT gene was preceded by a potential Shine-Dalgarno sequence. The gtfT gene product, glucosyltransferase (GTF), displays a typical gram-positive bacterial signal peptide sequence and both an active site peptide sequence and carboxy-terminal repeats typical of GTFs. The signal sequence is similar to those of other known GTF proteins. The putative active-site peptide sequence of this enzyme was DGIRVDAVD, which was different by one amino acid from the active-site peptide sequence derived from two different types of the S. sobrinus GTFs reported previously (G. Mooser, S. A. Hefta, R. J. Paxton, J. E. Shively, and T. D. Lee, J. Biol. Chem. 266:8916-8922, 1991). The gtfT gene product has three repeated sequences of 51 to 52 amino acids and a partial repeat of 18 amino acids. Another open reading frame (ORF) was detected in the region immediately upstream of the gtfT gene. The upstream ORF showed substantial DNA homology with the gtfS gene isolated from Streptococcus downei MFe28. The inferred amino acid sequence of the upstream ORF has four repeating units and has extensive homology with the repeated peptides coded by the S. downei gtfS gene. These results suggested that the gtfT gene was a typical gtf gene isolated from the mutans streptococci and that the two gtf genes were located in tandem on the chromosomal DNA of S. sobrinus OMZ176.

Amino Acid Sequence↗