Abstract
The storage polyglucan in cyanobacteria has been generally considered to be glycogen. Screening of 57 cyanobacterial strains revealed, however, that 4 had polysaccharide distinct from the typical cyanobacterial glycogen. From one such strain, Synechocystis aquatilis SI-2, polyglucan was extracted, debranched with isoamylase, and analyzed by capillary electrophoresis. The proportion of DP (degree of polymerization) ≤ 8 for Synechocystis sp. PCC 6803 and S. aquatilis was > 30 % and 15 %, while that of DP ≥ 37 was < 1 % and 4.5 %, respectively. The polyglucan preparations dissolved in alkali were subjected to size-exclusion chromatography (Sephacryl S-1000SF). The polyglucan of S. aquatilis was eluted faster than glycogen of strain 6803 and at the same position as amylopectin from rice endosperm. Three distinct genes encoding branching enzyme were identified in S. aquatilis, as opposed to the presence of the single gene in all known cyanobacteria.
