Comparative Composition of the Sheath of the Cyanobacterium Gloeothece ATCC 27152 Cultured with and without Combined Nitrogen

SUMMARY: The extracellular sheath was isolated from cultures of a unicellular diazotrophic cyanobacterium, Gloeothece ATCC 27152. Chemical analysis of lyophilized cell-free preparations indicated that the sheath was composed of an acidic heteropolysaccharide containing the neutral sugars rhamnose, 2-O-methylxylose, xylose, mannose, galactose and glucose, and the uronic acids mannuronic, glucuronic and galacturonic acid. Protein, pyruvic acid and O-acetyl and sulphate groups were also detected. Quantitative differences in the carbohydrate and protein content of the sheath were observed between material collected from cultures grown with and without a source of combined nitrogen. The extent to which the external layers bound cadmium ions was affected by these differences.