Characterization of a Cytoplasmic Reserve Glucan from Ruminococcus albus

Ruminococcus albus, an anaerobic bacterium that digests cellulose in the rumen of cattle, produces intracellular polysaccharide granules varying from 0.05 to 0.31 mum in diameter when grown in batch culture. This polysaccharide material was purified and found to contain d-glucose as the only reducing sugar. The polyglucose polymer was slightly opalescent in aqueous solution and formed a strong reddish purple iodine complex with a maximum absorbance at 550 nm. Its infrared spectrum had characteristic absorption bands at 8.70, 9.25, and 9.75 mum and was identical with that of the amylopectin-glycogen type of Megasphaera elsdenii and that of the glycogen of enteric bacteria and beef liver. It reacted strongly with concanavalin A. Methylation analysis showed that the glucan contained 2,3,4,6-tetra-O-MeG-2,3,6-Tri-O-MeG-2,3-Di-O-MeG in a ratio of 8:84:8. Characterization of the products obtained by treatment with isoamylase indicates that the glucan of R. albus is of the glycogen type.