Structural Characterization of the Released Polysaccharide of Desiccation-Tolerant Nostoc communeDRH-1

ABSTRACT The structure of the viscous extracellular polysaccharide (glycan) of desiccation-tolerant Nostoc commune DRH-1 was determined through chromatographic and spectroscopic methods. The polysaccharide is novel in that it possesses a 1-4-linked xylogalactoglucan backbone with d-ribofuranose and 3-O-[(R)-1-carboxyethyl]-d-glucuronic acid (nosturonic acid) pendant groups. The presence ofd-ribose and nosturonic acid as peripheral groups is unusual, and their potential roles in modulating the rheological properties of the glycan are discussed. Nosturonic acid was present in the glycans of N. commune from diverse geographic locations, suggesting that this uronic acid is an integral component of this cosmopolitan anhydrophile.

IMMUNOCHEMICAL STUDY OF A BACTERIAL ENDOTOXIN: SHIGELLA FLEXNERI TYPE Z

The endotoxins of the Gram-negative bacteria have similar biological and chemical properties. The toxic antigen of Shigella flexneri Type Z was selected as a representative endotoxin, and it was confirmed that the antigen consists of a polysaccharide conjugated with phospholipid and protein. By the technique of zone electrophoresis, the polysaccharide of the purified endotoxin was shown to be conjugated with each of three different proteins, and each conjugate proved toxic and antigenic for the rabbit. Two of the protein conjugates were digested by trypsin and the released polysaccharide appeared to conjugate with the remaining trypsin-resistant protein. Immunological analysis revealed that the purified toxic antigen is heterogeneous and that the polysaccharide and protein components possessed serological activity. The trypsin-treated toxin had a single electrophoretic zone and its precipitation in gel suggested immunological purity. Proteolytic treatment of the endotoxin did not destroy its toxicity or antigenicity for the rabbit.