Polysaccharides bacteria

As the most important skeletal component in plants and also a substance produced by certain bacteria, polysaccharide cellulose is an almost inexhaustible polymeric raw material with a fascinating structure and interesting properties. The fusion of both carbohydrate and polymer chemistry in a macromolecule biosynthetically composed of repeating glucose units generates surprising specificity and impressively diverse supramolecular/morpho-logical structures, reactivities, and functions. 

It is difficult to state whether formation of exocellular polysaccharides is more prevalent among the bacteria, the yeasts, or the molds. However, with bacteria, polysaccharide formation has been studied the most thoroughly. Several yeasts are known to elaborate exopolysaccharides and are excellent sources thereof. Polysaccharide formation by fungi is less frequently observed. However, species of... 

Fructofuranose is found in probably the most well-known and commercially available of all carbohydrates, sucrose. Various derivatives of sucrose are also known in nature, e.g. fatty acid derivatives [91] and agrocinopines [92]. Fructo-furanosides are also present in various plant and bacteria polysaccharides, most often as fructans, but sometimes as a singular component in repeating units [2, 93]. Syntheses of sucrose or derivatives thereof are not very frequent [41, 94-96], and oligosaccharide synthesis with fructofuranosyl donors are even more scarce. 

Particulate material can also be sampled from natural waters by direct collection onto vertical or horizontal plates (glass, Teflon, or other plastics) inserted for a while in the water column. Horizontal plates collect sedimenting particles without the drawbacks of conventional sediment traps (shifts in biological activity and redox conditions due to the absence of mixing at the bottom of the trap) vertical plates selectively collect those entities exhibiting a certain affinity for the plate (e.g., adhering bacteria, polysaccharides, Fe-oxyhydroxides). 

LASIK Y. and GORDIYENKO S.A. 1977. (Complexing of soil bacteria polysaccharides with metals). Soviet Soil Science translated from Pochvovedenie, 1977, 92-98. 

Also other polysaccharides containing carboxyl and amino groups such as chondroitin sulphate, dermatan sulphate N-carboxymethyl diitosan, and some bacteria polysaccharides may be used in a similar manner to build up ultrathin coatings on smfaces with defined attachments and mean thickness. 

Agar, which is low in metabolizable or inhibitory substances, debris, and thermoduric spores, is ideal for the propagation and pure culture of yeasts, molds, and bacteria. Agar also meets the other requirements of ready solubiUty, good gel firmness and clarity, and a gelation temperature of 35—40°C and a gel melting temperature of 75—85°C. A clarified and purified form of the bacterial polysaccharide, geUan gum, is the only known satisfactory substitute. 

Xanthan gum [11138-66-2] is an anionic heteropolysaccharide produced by several species of bacteria in the genus Aanthomonas A. campestris NRRL B-1459 produces the biopolymer with the most desirable physical properties and is used for commercial production of xanthan gum (see Gums). This strain was identified in the 1950s as part of a program to develop microbial polysaccharides derived from fermentations utilizing com sugar (333,334). The primary... 

The above chemicals can be obtained by fermentation (qv) of other sugars. However, some compounds require sucrose as a unique feedstock. Examples are the polysaccharides dextran, alteman, andlevan, which are produced by specific strains of bacteria (48,54—56). Dextrans are used to make chromatographic separation media, and sulfated dextran derivatives are used as plasma extenders (41). Levans show promise as sweetness potentiators and, along with alteman, have potential as food thickeners and bulking agents in reduced-caloric foods (55,56) (see Carbohydrates). 

Fiber components are the principal energy source for colonic bacteria with a further contribution from digestive tract mucosal polysaccharides. Rate of fermentation varies with the chemical nature of the fiber components. Short-chain fatty acids generated by bacterial action are partiaUy absorbed through the colon waU and provide a supplementary energy source to the host. Therefore, dietary fiber is partiaUy caloric. The short-chain fatty acids also promote reabsorption of sodium and water from the colon and stimulate colonic blood flow and pancreatic secretions. Butyrate has added health benefits. Butyric acid is the preferred energy source for the colonocytes and has been shown to promote normal colonic epitheUal ceU differentiation. Butyric acid may inhibit colonic polyps and tumors. The relationships of intestinal microflora to health and disease have been reviewed (10). 

Lipoteichoic acids (from gram-positive bacteria) [56411-57-5J. Extracted by hot phenol/water from disrupted cells. Nucleic acids that were also extracted were removed by treatment with nucleases. Nucleic resistant acids, proteins, polysaccharides and teichoic acids were separated from lipoteichoic acids by anion-exchange chromatography on DEAE-Sephacel or by hydrophobic interaction on octyl-Sepharose [Fischer et al. Ear J Biochem 133 523 1983]. 

Cell wall Peptidoglycan a rigid framework of polysaccharide cross-linked by short peptide chains. Some bacteria possess a lipopolysaccharide- and protein-rich outer membrane. Mechanical support, shape, and protection against swelling in hypotonic media. The cell wall is a porous nonselective barrier that allows most small molecules to pass. 

As shown in Figure 9.24, the outer membrane of Gram-negative bacteria is coated with a highly complex lipopolysaccharide, which consists of a lipid group (anchored in the outer membrane) joined to a polysaccharide made up of long chains with many different and characteristic repeating structures... 

FIGURE 9,24 Lipopolysaccharide (LPS) coats the outer membrane of Gram-uegative > bacteria. The lipid portion of the LPS is embedded iu the outer membrane and is linked to a complex polysaccharide. 

Lysozyme is an enzyme that hydrolyzes polysaccharide chains. It ruptures certain bacterial cells by cleaving the polysaccharide chains that make up their cell wall. Lysozyme is found in many body fluids, but the most thoroughly studied form is from hen egg whites. The Russian scientist P. Laschtchenko first described the bacteriolytic properties of hen egg white lysozyme in 1909. In 1922, Alexander Fleming, the London bacteriologist who later discovered penicillin, gave the name lysozyme to the agent in mucus and tears that destroyed certain bacteria, because it was an enzyme that caused bacterial lysis. 

A lipopolysaccharide (LPS) is any compound consisting of covalently linked lipids and polysaccharides. The term is used more frequently to denote a cell wall component from Gram-negative bacteria. LPS has endotoxin activities and is a polyclonal stimulator of B-lymphocytes. 

This class of polysaccharide was well known in sugar refineries as the causative agent of ropiness it was formed from cane or beet sugar by bacteria of the Leuconostoc genus. Over many years, numerous papers were published, mainly with E. J. Bourne [Adv. Carbohydr. Chem. Biochem., 34 (1977) 1-22] and S. A. Barker as co-authors, describing the isolation, purification, properties, and structural features of dextrans. 

L-Fucosamine was found as a constituent of Pneumococcus Type V capsular polysaccharide and as a constituent of the mucopolysaccharides (glycosamino-glycans) of certain enteric bacteria A new synthesis was devised to make the amino sugar more available. 

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