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Rare amino sugars in exopolysaccharides (EPS) from cyanobacteria of the genus Synechocystis
Amino sugars are widely spread in natural polysaccharides, e.g. chitin in fungi, glycosaminoglycans in animals and lipopolysaccharides (LPS) in gram negative bacteria . The most common amino sugars are N-acetyl-glucosamine and N-acetyl-galactosamine which also have been detected in cyanobacterial EPS . The amino sugar N-acetyl-fucosamine (2-acetamido-2,6-dideoxy-D-galactose) has been found in the LPS of some gram negative bacteria. For the first time we identified a 2-N-acetyl-amino-2,6-dideoxy-hexose, propably N-acetyl-fucosamine, in EPS of Synechocystis aquatilis SAG 90.79. This EPS consists of only four sugars: 46% fucose, 37% arabinose, 12% amino hexose and 2% glucose independent on the conditions of cultivation. In contrast the EPS of Synechocystis pevalekii SAG 91.79 with more than seven sugars is more typical for cyanobacterial EPS . It contains 24% mannose, 23% glucose, 12% fucose, 11% galactose, 9% xylose, 7% rhamnose and 4% of a newly found 2-amino-2-deoxy-pentose. A special feature of both EPS is the absence of uronic acids. They have an average sulphate content of about 20% and both can be separated into 4 to 5 fractions by ion exchange chromatography. The occurrence of amino deoxysugars accessorily points out the classification of cyanobacteria to the group of gram negative bacteria .
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