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PubMed1977

Extracellular dextran hydrolase from Streptococcus mutans strain 6715.

Streptococcus mutans strain 6715 was shown to produce an extracellular dextramase with endohydrolytic alpha-(1 leads to 6)-glucan-6-glucanohydrolase activity. The enzyme degraded soluble polymers produced by some oral streptococci but did not disperse the streptococcal plaques tested. Enzyme levels in the culture supernatant were elevated in sucrose and sucrose plus glucose cultures but remained at basal levels in glucose and dextran plus glucose cultures.

Chromatography, Gel↗
PubMed1977

Measurement and synthesis of insoluble and soluble dextran by Streptococcus mutans.

Total and insoluble dextransucrase activities of 10 strains of oral streptococci were measured by a modified filter disk assay. Strains that were nonadherent to hard surfaces had only low levels of insoluble dextransucrase activity. A physical rather than metabolic mechanism is suggested to explain the decreased insoluble and increased soluble activities observed when dextran T-10 is added to the media.

Bacteriological Techniques↗
PubMed1979

Clinical studies of plaque control agents: an overview.

Dental plaque is massed packed bacterial cells which accumulate on the supra- and subgingival surfaces of the teeth as well as on the oral mucosa. The microorganisms of plaque have been shown to be associated with both dental caries and periodontal disease. This overview of clinical studies of plaque control agents reviews the properties and effects of chemical compounds which have demonstrated a potential for the control of plaque microorganisms. The search for clinically effective antiplaque agents has been stimulated by findings in laboratory and animal studies of plaque dynamics. Based upon these in vitro and in vivo experiments, chemotherapeutic agents such as antibiotics, antiseptics, enzymes, detergents, bacteriosides, antimetabolites, and oxidizing agents have been evaluated against human plaque microorganisms using the ultimate biological model -- man. Continued study of chemotherapeutic agents should be encouraged because many of these drugs have been shown to be safe for human use and may require only the development of a delivery system to potentiate their concentration in a specific local site. Use of these chemotherapeutic agents, which can be self-administered, becomes an attractive way of providing the public with a cost-effective method of preventing caries and periodontal disease.

Animals↗
PubMed1980

Composition and metabolic activity of dental plaque from healthy young and elderly individuals.

The composition and biochemical activities of 4- and 9-day-old plaque were studied in young and elderly subjects. Plaque accumulation tended to be greater in the older group. Levan hydrolase activity and the total number of recoverable, viable microorganisms were higher in plaque from younger subjects. Results suggest that the microbial composition of plaque is qualitatively different in younger and elderly subjects.

Adult↗
PubMed1984

Activity of Streptococcus mutans alpha-D-glucosyltransferases released under various growth conditions.

The effect of a variety of growth conditions on extracellular D-glucosyltransferase (GTF) activity of Streptococcus mutans strains in continuous culture has been studied. Maximum GTF activity was found at low growth rates and at pH 6.5, and under this condition the predominant glucosyltransferase was GTF-S, an enzyme that synthesized soluble dextran. At high growth rates, the proportion of GTF-S decreased, and 50% or more of the total glucosyltransferase was GTF-I, an enzyme that synthesized water-insoluble (1 leads to 3)-alpha-D-glucan. Variation in the relative activities of GTF-S and GTF-I results in such diversity in the glucans synthesized from sucrose that it is virtually meaningless to describe a structural analysis of S. mutans glucan without specifying the conditions of growth of the organism.

Culture Media↗
PubMed1987

Ultrastructure of extracellular polysaccharides produced by serotype c Streptococcus mutans.

The ultrastructure of extracellular polysaccharides produced in colonies by two clinical isolates and that of a nitrosoguanidine-induced mutant of serotype c Streptococcus mutans with different polysaccharide-synthesizing abilities were compared electron-microscopically. A large amount of polysaccharide was produced from sucrose by colonies of typical serotype c strain MT8148R and a clinical variant MT6801R with an enhanced fructan-synthesizing ability. Transmission electron-microscopy (TEM) revealed that the polysaccharides consisted of three structural components, i.e., globular, single-stranded filamentous, and double-stranded fibrillar structures. These structures were ascribed to production of fructan, water-soluble glucan, and water-insoluble glucan, respectively. On the other hand, two kinds of structures, a globular body and an amorphous substance, were observed by scanning electron-microscopy (SEM). The former was composed of fructan, while the latter contained a mixture of water-soluble and water-insoluble glucans which formed filamentous and double-stranded fibrillar structures under TEM. Very small quantities of polysaccharides were formed in colonies of mutant NG7183, which was derived from S. mutans MT6801R. This strain was found to possess low glucan- and no fructan-synthesizing abilities. The polysaccharides produced in colonies of mutant NG7183 were composed only of filamentous and double-stranded fibrils under TEM. A small amount of amorphous substance was observed by SEM in colonies of NG7183.

Dextranase↗
PubMed1976

Dextran degrading bacteria in human oral cavity and their activity against insoluble glucan from Streptococcus mutants.

The distribution of dextran-degrading microorganisms in the saliva and plaque samples from the human oral cavity was assayed on 9 subjects. Approximately 2/3 of the saliva samples degraded Dextran T-150 (Pharmacia, M.W. 150,000) and 1/10 the Blue Dextran (Pharmacia), while 2/5 and 1/8 of the plaque samples degraded Dextran T-150 and Blue Dextran, respectively. Thirty-seven strains of the Blue Dextran degrading bacteria were isolated from the saliva and plaque samples and were classified into 6 groups by their morphology, gram staining and oxygen tolerance. The 24 strains from the 37 isolates, more or less, were shown to degrade the insoluble glucan extracted from Streptococcus mutans FA-1 on the agar plate. The 8 strains, selected from each group, were tested for their activity against the insoluble glucan extracted from Str. mutans (FA-1, HS-6, BHT, CHT, GS-5, LM-7 and PK-1) and Str. salivarius (HHT). The strains belonging to Groups I, II, IV and V showed activity against the insoluble glucan used. Among them, the strains of Group IV (gram negative facultative cocci) and Group V (gram negative strict anaerobic rod) were the most active against the insoluble glucan.

Adult↗