Dextrans, bacterial

Microbial Polysaccharides Bacterial polysaccharide bacterial cellulose, dextran, bacterial hyaluronic acid, xanthan, emulsan, p-d glucans, curdlan, alginate, gellan and pullulan, scleroglucan and schizophyllan. bacterial hyaluronic acid, kefiran, exopolysaccharide, xanthan gum, dextran, welan gum, gellan gum, diutan gum and pullulan... 

Bacterial Dextrans, M. Stacey and C. R. Ricketts, Fortschr. Chem. Org. Naturstoffe, Springer-Ver-lag Wien, 8 (1951)28-46. 

Dextran is the collective name of extracellular bacterial poly-alpha-D-glucopyranoses linked largely by 1,6 bonds, with branching occurring at the 1,2, 1,3 or 1,4 bonds. Physical properties vary... 

Bacterial cellulose, dextran and many other bacterial polysaccharides are composed entirely of D-glucose units the levans are condensation polymers of D-fructose. Dextrans from different species of Leuconostoc... 

Fitzgerald42 found that the antibody response of rabbits toward 1.5% aqueous dextran solutions (both types) varied with the nitrogen (t. e., bacterial) content of the dextran. Injections were administered both interperitoneally and intravenously, and no antibody production resulted when the nitrogen content of the dextrans was below 0.2%. 

The structures of a number of other bacterial polysaccharides resembling the dextrans have been investigated. 

Morita, H. (1956b). The differential thermal properties of bacterial dextrans. Journal of the... 

In addition to murein, bacterial polysaccharides include dextrans—glucose polymers that are mostly al 6-linked and al 3-branched. In water, dextrans form viscous slimes or gels that are used for chromatographic separation of macromolecules after chemical treatment (see p.78). Dextrans are also used as components of blood plasma substitutes (plasma expanders) and foodstuffs. 

The main product of anaerobic degradation of sugars by these organisms is lactic acid. Other products of bacterial carbohydrate metabolism include extracellular dextrans (see p. 40)—insoluble polymers of glucose that help bacteria to protect themselves from their environment. Bacteria and dextrans are components of dental plaque, which forms on inadequately cleaned teeth. When Ca salts and other minerals are deposited in plaque as well, tartar is formed. 

Myeloma proteins occur in animal tumors of various types. The synthesis of these proteins can be induced in some experimental animals by injection of mineral oil, or the implantation of plastic discs.161 Myeloma proteins were shown to possess antibody activity, with specificity for different types of substances.161 Some of these proteins were found to combine with such carbohydrates as bacterial, cell-wall polysaccharides, lipopolysaccharides, dextrans, levans, and galactans.162 Myeloma proteins that combine with galactans or dextrans possess anti-galactan activity,163,164 or anti-dextran activity,165-167 and have been studied most extensively. 

Dextrans are bacterial and yeast polysaccharides made up of (a 1—>6)-linked poly-D-glucose all have (al—>3) branches, and some also have (al—>2) or (al—>4) branches. Dental plaque, formed by bacteria growing on the surface of teeth, is rich in dextrans. Synthetic dextrans are used in several commercial products (for example, Sephadex) that serve in the fractionation of proteins by size-exclusion chromatography (see Fig. 3-18b). The dextrans in these products are chemically cross-linked to form insoluble materials of various porosities, admitting macromolecules of various sizes. 

Sucrose and Dental Caries The most prevalent infection in humans worldwide is dental caries, which stems from the colonization and destruction of tooth enamel by a variety of acidifying microorganisms. These organisms synthesize and live within a water-insoluble network of dextrans, called dental plaque, composed of (al 6)-linked polymers of glucose with many (a 1 >3) branch points. Polymerization of dextran requires dietary sucrose, and the reaction is catalyzed by a bacterial enzyme, dextran-sucrose glucosyltransferase. 

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