Re-examination of cellular cyclic β-1,2-glucans of Rhizobiaceae: Distribution of ring sizes and degrees of glycerol-1-phosphate substitution

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Abstract
Gel-filtration and thin layer chromatography of low molecular weight carbohydrates from culture filtrates of Agrobacterium radiobacter, Isolate II, have shown, that next to the neutral β-1,2-glucan fraction a major acidic fraction was present which was found to be glycerophosphorylated cyclic β-1,2-glucans. Re-examination of cyclic β-1,2-glucan preparations which had been obtained by extraction of Rhizobium cells with hot phenol-water also showed these acidic modified β-1,2-glucans to be present. Cyclic β-1,2-glucans from R. leguminosarum (9 strains) and of R. phaseoli (1 strain) had ring size distribution with degrees of polymerisation (DPs) of 19 and 20 as major ring sizes of which a minor part was glycerophosphorylated; β-1,2-glucans of R. trifolii (3 strains) had ring sizes with DPs measuring 19–22 as prominent components which were largely unsubstituted, and R. meliloti (7 strains) had β-1,2-glucans with ring size distributions extending to still higher DPs of 19–25 of which the major part appeared to be glycerophosphorylated.