Soil saccharides

General Conclusions from Studies of Soil Saccharides 25... 

Interest in soil saccharides, and especially in soil polysaccharides, is relatively recent, and their studies may be considered to be in the modern era of soil organic matter research. Martin (1945,1946) established that the slimy bacterial products... 

There is a need to resume studies of soil saccharides and peptides. These can compose as much as 30-40% (when account is taken of the compositions of humin materials). Much is known about how polysaccharides of known structures interact with soil colloids, but it has not been possible as yet to know in sufficient detail the structures of the polysaccharides that persist in the soil. Hence we do not know the mechanisms of their binding to soil mineral colloids. The same applies for the peptide materials, though it is clear that polysaccharides and peptides have important roles in soil structure formation and stabilization. 

The example of a total extract composition of a tropical soil from the Amazon, Brazil, shows mycose as the major compound, numerous other monosaccharides, lipid components such as fatty acids and fatty alcohols, and natural product biomarkers (Fig. 9a). The mycose and elevated levels of the other saccharides reflect the efficient fungal/microbial degradation of plant detritus in the tropics. This can be compared to the saccharides in the soil from an almond orchard in California, where glucose and mycose are the main sugars with lipids, sterols and triterpenoids (Fig. 9b, ). 

The book by Cheshire (1979) has reviewed studies of soil polysaccharides, and he and his colleagues have contributed significantly to our awareness of the subject. Chapters by Hayes and Swift (1978), Cheshire and Hayes (1990), and Clapp et al. (2005) have reviewed relevant aspects of the chemistry and compositions of polysaccharides and have discussed the reactivities of saccharides in the soil environment. 

The bulk of the saccharides in soil aqueous extracts are contained in the FA fraction, or the organic fraction that remains in solution on acidification of soil extracts. The introduction of XAD resin technology (see Section 1.3.2) for the fractionation of soil organic extracts has allowed some separation of saccharides from what are considered to be the true FAs. Swincer et al. (1968) deserve to be credited with that concept. They used Polyclar-AT [a (poly)vinylpyrrolidone resin used for... 

South-American soil was a good source [54] of S. curacoi producing the antibiotic curamycin (58). This antibiotic also contains unusual saccharides, i.e. L-lyxose and 4-O-methyl-D-fucose. 

Avilamycin A (59) isolated [55] from S. viridochromogenes collected from a Venezuelan soil sample, exhibits similar effects. Its structure was elucidated by NMR methods and two unusual saccharides - evalose and evermicose - were identified in the sugar moiety. 

Zelles, L., Q.Y Bai, T. Beck, F. Beese. 1992. Signature fatty acids in phospholipids and lipopoly-saccharides as indicators of microbial biomass and community structure in agricultural soils. Soil Biology and Biochemistry 24 317-323. 

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