THE STRUCTURE AND RESISTANCE TO METHYLATION OF 1,2-β-GLUCANS FROM SPECIES OF AGROBACTERIA

Abstract

The structures of extracellular polysaccharides produced by the plant pathogens Agrobacterium tumefaciens (2 strains), A. rhizogenes, A. radiobacter, A. ruhi, A. gypsophilae, and A. pseudotsugae were investigated. Polymeric material was formed in good yield from all organisms except A. gypsophilae. Periodate oxidations of the polysaccharides and their sodium borohydride reduction products indicated linear 1,2-glucopyranose structures for A. tumefaciens (2 strains), A. rhizogenes, A. radiobacter, and A. rubi polymers. Optical rotational considerations led to the assignment of β-configurations. The linear structure for the A. radiobacter polysaccharide was confirmed by the isolation, after partial acid hydrolysis, of five 1,2-linked oligosaccharides with chain lengths of two to six. Periodate and chromatographic data indicated that the polysaccharide from A. pseudotsugae contained glucose and galactose and 1,6- as well as 1,2-glycopyranose links. It is noteworthy that the polysaccharides from the genus Agrobacteriurm are shown to be mainly 1,2-β-glucans, a structure not yet found in other genera.Treatment of linear 1,2-β-glucans from A. tumefaciens, A. radiobacter, and A. rhizogenes with sodium hydroxide – dimethyl sulphate, followed by silver oxide in methyl iodide dimethyl formamide, did not cause full methylation. Some of the 3-hydroxyl groups were not substituted and possible reasons for this unreactivity are discussed.