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At least 127 records · Page 7Linked to original sources
PubMed1985

Lactic acid production by oral Streptococcus mitis inhibits the growth of oral Capnocytophaga.

Various relationships including inhibition or stimulation of growth have been demonstrated among the bacteria present in dental plaque, both in vitro and in vivo. A large number of these relationships involved oral Streptococci. An earlier study found that strains of Streptococcus mitis inhibited the growth of potential periodontopathic microorganisms, such as Actinobacillus actinomycetemcomitans, Capnocytophaga and species of Bacteroides and Fusobacterium. The present investigation showed that this inhibitory effect resulted primarily from lactic acid production.

Bacteroides↗
PubMed1996

A flexible model for the cell wall polysaccharide of Streptococcus mitis J22 determined by three-dimensional 13C edited nuclear overhauser effect spectroscopy and 13C-1H long-range coupling constants combined with molecular modeling.

We report on the conformation of a tetrasaccharide fragment in the repeating subunit of the cell wall polysaccharide of Streptococcus mitis J22, a receptor for the lectin of Actinomyces viscosus T14V in a bacterial coaggregation that is important in the ecological interactions of oral bacteria. Although there is considerable overlap of the 1H-nmr signals, some cross peaks can be extracted from conventional two-dimensional nuclear Overhauser effect spectroscopy (NOESY) data on the polysaccharide. These data cannot be fit to a single conformation of the tetrasaccharide fragment. Therefore we have prepared a polysaccharide sample fully enriched in 13C from which we have determined accurate NOESY cross-peak volumes in a three-dimensional heteronuclear-resolved spectrum that allows accurate determination of many more NOESY cross peaks than does conventional two-dimensional spectroscopy. We have also used the 13C enriched polysaccharide to measure accurate values of long-range 13C-1H coupling constants that can be correlated with glycosidic dihedral angles. Molecular modeling calculations on the polysaccharide fragment, including molecular dynamics simulations, identify multiple low-energy conformations. This result is to be contrasted with previous calculations on blood group oligosaccharides in our laboratory using similar methods that showed relatively rigid conformations with little flexibility of the glycosidic linkages. The present NOESY and 3JCH data can be reconciled with a model for the antigenic tetrasaccharide in which three distinct conformations are in fast exchange. We propose that some carbohydrate epitopes such as those of the blood group oligosaccharides are relatively rigid while others such as the tetrasaccharide fragment in these studies exhibit much greater flexibility.

Carbohydrate Conformation↗
PubMed1995

Clonal diversity of the Streptococcus mitis biovar 1 population in the human oral cavity and pharynx.

A total of 250 isolates of oral streptococci were recovered from swabs of oropharyngeal surfaces of 3 members of one family. All isolates were examined by biochemical and serological means, and 106 isolates were identified as Streptococcus mitis biovar 1. These were typed by restriction endonuclease analysis using the enzymes EcoRI and HaeIII and further characterized by their whole-cell polypeptide profile patterns in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In addition, rabbit antisera raised against 8 reference strains of oral streptococci were used to characterize representative isolates both by their carbohydrate and protein antigens by Ouchterlony and Western blot analyses. Very limited biochemical diversity was observed among the 106 S. mitis biovar 1 isolates. In contrast, 24 different genotypes defined by restriction endonuclease analysis were detected, and each individual carried 6-13 types. Limited sharing of genotypes was observed between the 3 members of the same family and between the pharyngeal and buccal mucosa of single individuals. The antigenic analyses showed remarkable antigenic diversity between the 24 genotypes. The results provide a basis for studying the population dynamics of an oral commensal species and its interaction with the salivary immune system.

Adult↗
PubMed1999

The phenomenon of salivary protein adsorption onto Streptococcus mitis ATCC 903 cells.

It is thought that salivary proteins on bacterial cells have some influence on the adhesion of oral bacteria onto the surface of oral tissues and on bacterial aggregation. Initially, this study sought to examine the phenomenon of salivary protein adsorption to the surface of Streptococcus mitis ATCC 903 using 3H-labeled salivary proteins. We investigated the effects of hydrophobic level and lectin-ligand binding on adsorption of salivary proteins, and also the influence of cell surface components on adsorption. The results showed that the adsorption of salivary proteins was clearly reduced by the presence of Tween 20, LiCl, NaSCN, Hexadecane and some sugars. The adsorption was also affected by the pH level, and protease treatment or heat treatment of cells also decreased the volume of adsorbed proteins. Although the adsorption of proteins onto heat-treated cells was dramatically reduced by the presence of LiCl and NaSCN, the presence of sugars had little influence on this adsorption. These findings suggest that the main adsorption of salivary proteins is due to hydrophobic factors, and the heat-sensitive surface components of the cells had some relation to lectin-ligand binding. Therefore, it appears important to study the adsorption of salivary proteins onto cells since the salivary proteins on bacterial cells play an important role in their adherence to the saliva-coated oral tissues and bacterial aggregation.

Adsorption↗
PubMed1983

Trimethylsilyl-sugar profiles of Streptococcus milleri and Streptococcus mitis.

Seventy strains of 'viridans-group' streptococci were analysed gas chromatographically after preparation of trimethylsilyl ethers of their cellular sugars. The resulting profiles were evaluated as a possible aid to taxonomy. Glycerol, glucose, galactose, N-acetyl-glucosamine and N-acetylmuramic acid were found in all strains, in varying amounts. Rhamnose was the major neutral sugar in most strains, other than representatives of Streptococcus mitis, which invariably had ribose and usually anhydroribitol but no rhamnose. One strain of Strep. mitis possessed arabitol. Some strains of Strep. mitis and 'Strep. milleri' were alone in containing N-acetylgalactosamine. A combination of N-acetylgalactosamine and rhamnose in the absence of ribose was diagnostic for strains of 'Strep. milleri'.

Acetylgalactosamine↗
PubMed1998

Whole-cell protein electrophoretic analysis of viridans streptococci: evidence for heterogeneity among Streptococcus mitis biovars.

One hundred reference strains representing all species belonging to the different phylogenetic lineages of the viridans streptococci were examined by means of one-dimensional whole-organism protein electrophoresis. For most of the species examined, multiple strains characterized by DNA-DNA hybridization were included and, wherever described, representatives of different biochemical variants were analysed. Most species were clearly differentiated. The data support the viewpoint that members of the Streptococcus anginosus group constitute a single species and indicate that Streptococcus mitis biovar 2 is a heterogeneous taxon comprising strains from several streptococcal species.

Bacterial Proteins↗
PubMed2002

Softness of the bacterial cell wall of Streptococcus mitis as probed by microelectrophoresis.

Chemical and structural complexity of bacterial cell surfaces complicate accurate quantification of cell surfaces properties. The presence of fibrils, fimbriae or other surface appendages on bacterial cell surfaces largely influence those properties and would therefore play a major function in interfacial phenomena as aggregation and adhesion. The electrophoretic softness and fixed charge density in the polyelectrolyte layer of nine Streptococcus mitis strains, usually carrying long sparsely distributed fibrils, were determined by the soft particle analysis using measured electrophoretic mobilities as a function of the ionic strength. In general, S. mitis cell surfaces are electrophoretically soft (1.0-2.5 nm) with a fixed negative charge density of -1.2 to -4.3 x 10(6) Cm(-3). Further, a comparison with surfaces of other bacterial strains that are reported to be soft indicates that the Ohshima soft layer model does not provide information on the surface morphology causing the softness. The most likely reason is that the electroosmotic flow occurs only in the very outer region of thick extracellular surface layers. Nevertheless, determining the surface softness is essential for proper characterization of the cell surface electrostatics.

Cell Wall↗
PubMed1997

Arg-Gly-Asp(RGD) peptides inhibit Streptococcus mitis to adhere to fibronectin.

Fibronectin (Fn) is a multifunctional adhesive protein found on cell surfaces as well as in plasma. It is also believed to play an important role in bacterial adherence to host tissues. Molecular analyses of Fn have shown that the amino acid triplet arginine-glycine-aspartic acid (RGD) sequence functions as a binding site. We examined the role of the RGD sequence on bacterial adherence to Fn. The pretreatment of Streptococcus mitis with synthetic RGD-containing peptide reduced the number of bound bacteria to the Fn coated plates by 76%. In contrast, a control peptide containing the RGE sequence showed no inhibition. These data indicate that synthetic RGD peptides may be useful for the inhibition of bacterial adherence to Fn on host cell surfaces.

Amino Acid Sequence↗
PubMed1999

New strategy for the conformational analysis of carbohydrates based on NOE and 13C NMR coupling constants. Application to the flexible polysaccharide of Streptococcus mitis J22.

For complex oligosaccharides, which are relatively rigid with modest excursions from a single minimum energy conformation, it is straightforward to build conformational models from NOE data. Other oligosaccharides are more flexible with transitions between distinct minima separated by substantial energy barriers. We show that modeling based on scalar coupling data is superior to NOE-based modeling for the latter case. Long range 13C-13C and 13C-1H coupling constants measured for the heptasaccharide repeating subunit of the cell wall polysaccharide from Streptococcus mitis J22 are correlated with individual glycosidic dihedral angles, effectively uncoupling the degrees of freedom of the oligosaccharide and allowing a search for combinations of dihedral angles which are energetically reasonable, i.e., with no bad van der Waals contacts, and which can be combined to satisfy all the measured J values. Allowed values of the individual angles can then be combined to search for overall oligosaccharide conformations which contribute to the ensemble. We show that while the polysaccharide from S. mitis J22 is flexible, requiring multiple conformations, most of the flexibility is localized to a few bonds and only a rather small number of conformations is required to reproduce the experimental NOE and scalar coupling data.

Carbohydrate Conformation↗
PubMed1985

Genetic transformation in Streptococcus sanguis. Effects on genetic transformation by culture filtrates of Streptococcus sanguis (serogroups H and W) and streptococcus mitis (mitior) with reference to identification.

Streptococcus sanguis (serogroups H and W) strains are frequently competent in genetic transformation. In a collection of 18 strains of S. sanguis isolated from blood cultures, 12 strains were spontaneously competent in transformation by streptomycin-resistant DNA, and three strains were induced to competence by the use of culture filtrates containing competence factor (CF). Culture filtrates from spontaneously competent S. sanguis strains only induced competence in transformation of strains of the same species. In addition to the three "constitutional" types of S. sanguis with regard to specificity of transformation previously reported (originally represented by the strain Challis, 13b and NCTC 7863), a possible fourth type, (represented by strain 21452) was found. Further studies are required to ascertain the role of these types. The "constitutional" types are characterized by the range of activity of their CF's. These specificities seem useful in identification of S. sanguis and its separation from S. mitis (mitior). Tests of spontaneously competent strains with culture filtrates from other competent strains showed variable effects on the transformation frequencies in different strains.

Bacterial Proteins↗
PubMed1998

Streptococcus peroris sp. nov. and Streptococcus infantis sp. nov., new members of the Streptococcus mitis group, isolated from human clinical specimens.

Taxonomic studies were performed on eight strains of alpha-haemolytic streptococci that showed very low DNA-DNA hybridization similarity values with all established members of the mitis group of the genus Streptococcus. These strains were isolated from the tooth surface and pharynx of humans. 16S rRNA gene sequence analysis showed that these strains belonged to the mitis group, but that they fell into two new branches. DNA-DNA hybridization demonstrated two new similarity groups. From the results of the present study, the names Streptococcus peroris sp. nov. and Streptococcus infantis sp. nov. are proposed for these new groups. The type strains are O-66T (= GTC 848T = JCM 10158T) and O-122T (= GTC 849T = JCM 10157T), respectively.

Base Composition↗