Soil, polysaccharides

CLAPP C.E. and EMERSON W.W. 1972. Reactions between Ca-montmorilIonite and polysaccharides. Soil Science, 114, 210-216. 

By 1945, Stacey speculated about the possibility of a structural relationship between Pneumococcus capsular polysaccharides and those produced by other organisms. With Miss Schliichterer, he had examined the capsular polysaccharide of Rhizobium radicicolum. This polysaccharide gave a precipitin reaction in high dilution, not only with Type III Pneumococcus antiserum, but also mixed with antisera from other Pneumococcus types. The chemical evidence indicated that the polysaccharide resembled the specific polysaccharides of Types I and II Pneumococcus. A decade later, the acidic capsular polysaccharide from Azoto-bacter chroococcum, a soil organism, was studied. It, too, produced serological cross-reactions with certain pneumococcal specific antisera. Although the molecular structure of the polysaccharide was not established, adequate evidence was accumulated to show a structural relationship to Type III Pneumococcus-specific polysaccharide. This was sufficiently close to account for the Type III serological cross-relationship. 

Studies on Soil Polysaccharides and on Their Interaction with Clay Preparations. Soil Chemistry and Fertility, P. Finch, M. H. B. Hayes, and M. Stacey, (1966) Trans. Comm. II IV Int. Soc. Soil Sci., Aberdeen, G. V. Jacks, Ed. (1967) 19-32. 

It is sometimes claimed that mucilage and similar gels may help to maintain hydraulic conductivity between root and. soil (52). However, the hydraulic conductivity of soils is often substantially decreased when soils are irrigated with waste water. Apart from the inducement of sodicity, which is real in many cases, the decreases in hydraulic conductivity are attributed largely to the production of microbial biomass, particularly extracellular polysaccharides (e.g.. Ref. 53). These extracellular polysaccharides form gels that may store large quantities of water and allow water and ions to diffu.se through them at rates not much less than those of free water, but they could be expected to restrict mass flow of water and thus nutrients, to roots (54). 

Bacillus krzemieniewski(f). This soil bacillus forms thick, gelatinous capsules on carbohydrate media and yields a polysaccharide which on hydrolysis is stated to produce L-mannose.660 This claim is based upon the melting point of the isolated mannose phenylhydrazone and upon the rotation of the hydrolyzed reaction mixture. It requires further confirmation. 

Hot water-extractable C accounts for 1-5% of soil organic C (Leinweber et al. 1995 Sparling et al. 1998 Chan and Heenan 1999) and about 50% of this is thought to be present as carbohydrate (Haynes 2005). Because it is usually extracted from air-dried soils much of the pool originates from desiccated microbial cells but it also includes exocellular polysaccharides, root exudates, lysates and humic material (Redl et al. 1990 Leinweber et al. 1995 Sparling et al. 1998). Both hot water extractable C (Sparling et al. 1998 Chan and Heenan 1999) and hot water-extractable carbohydrate (Ball et al. 1996 Haynes and Beare 1997 Debrosz et al. 2002) have been used as indices of soil quality. 

A fraction of organic C oxidizable with 333 mM KMn04 is another measure of labile organic matter (Blair et al. 1995). This fraction encompasses all those organic components that can be readily oxidized by KMnCL including labile humic material and polysaccharides (Conteh et al. 1999). It commonly accounts for 15-20% of total soil organic C (Blair et al. 1998 Conteh et al. 1998). 

Fungal polysaccharides, 20 455, 577-578 Fungi. See also Soil fungi alkaloids in, 2 75... 

Polysaccharides are used as structural units and as stored energy sources. Proteins are used to construct muscle and enzymes that also contain metals such as zinc, manganese, and iron. There are many other important biomolecules present at lower concentrations such as DNA and RNA, which are also released into the soil solution. All can be the source of smaller molecules in the soil solution. 

The different groups of biomolecules, including fatty acids, triglycerides, polysaccharides, and proteins (illustrated in Figure 4.9) decompose at different rates depending on their composition. Lipids and fats are slower to decompose in soil because of their insolubility in water. Large polysaccharides are also insoluble in water but are more quickly decomposed than fats. Proteins and compounds such as DNA and RNA are more quickly decomposed in part... 

Abiontic, involving free extracellular enzymes or solubilizing agents, enzymes bound to soil surfaces, enzymes within dead or non-proliferating cells, or enzymes associated with dead cell fragments. Extracellular enzymes are important in the initial stages of organic matter oxidation, in which polysaccharides and proteins are hydrolysed to soluble compounds that can be absorbed by microbial cells and further oxidized in biotic processes. 

For the reasons stated above, deep intrusion of degrading microbes into polysaccharide-plastic films is demonstrably and theoretically improbable. Since starch removal does occur when the films are buried in soil, the primary mechanism must be microbial production of amylase in or near a pore, diffusion of the enzyme into pores and diffusion of soluble digestion products back to the surface where they are metabolized (Figure 3). This mechanism would be the only choice when the pore diameter is too small to admit a microbial cell (i.e., at diameters < 0.5 /im). An alternative mechanism could be diffusion of a water-soluble polysaccharide to the film surface, at which point degradation would occur. None of the materials used in these investigations showed loss of starch even when soaked in water for extended periods with microbial inhibitors present. Therefore, diffusion of amylase to the substrate rather than diffusion of the substrate to the film surface is the more likely mechanism. 

The scheme proposed above requires microbial colonization of the material and excludes degradation by amylases and cellulases that are present in soils (28), but are not newly synthesized or associated with microbial cells. Active polysaccharide hydrolases are found in nearly all soils, but these enzymes are primarily bound to soil organic matter or mineral components attachment is firm enough to severely limit migration of the enzymes from surrounding soil to the film. 

A fructan-produclng bacterium was Isolated from soils and characterized for polysaccharide synthesis. The composition and properties of the polysaccharide produced were studied. The organism. Identified as a strain of Bacillus polvmvxa. produced a large quantity of polysaccharide when grown on sucrose. 

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