CHAPTER XIX 



THE POLYSACCHARIDES OF MICRO- 

 ORGANISMS 



THE production of polysaccharides by micro-organisms 

 is almost as widespread and universal as that of the 

 proteins. Polysaccharides of a more or less degree 

 of complexity are to be found in nearly all bacteria, 

 yeasts and fungi. Of the common polysaccharides, 

 starch, cellulose and glycogen are found as the result 

 of the synthetic activities of micro-organisms, and 

 besides these a considerable number of other poly- 

 saccharides characteristic of particular organisms is 

 known. 



The chief poh^saccharide produced by yeasts is 

 glycogen, but others comprising the various " yeast 

 gums " have been described. Glycogen has also been 

 isolated from the higher fungi and from certain species of 

 Aspergillus. It has been claimed that it is also present in 

 certain bacteria, including Mycobacteriiim tiiherculosis, 

 CI. hutyricum and Shigella dysenterice. 



As was mentioned in Chapter V the presence of cellu- 

 lose in micro-organisms has been established satisfactorily 

 only in the case of Acetobacter xyUnum, in which it was 

 detected as early as 1886 by Brown. It is sjoithesised by 

 the cell from a variety of sugars, for example glucose, 

 fructose, sucrose and pentoses, and even more readily 

 from such polyhydric alcohols, with three to seven carbon 

 atoms, as glycerol, erythritol, arabitol, dulcitol, sorbitol, 



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