Molecular architecture of a galactoglucan from Rhizobium meliloti.

Rhizobium meliloti mutants produce a linear, acidic exopolysaccharide with alternating galactopyranosyl and glucopyranosyl units having (1-->3) linkages. It has a 4,6-O-pyruvic cyclic acetal group on the alpha-galactosyl and 6-O-acetyl ester group on the beta-glucosyl units. X-ray diffraction patterns from polycrystalline and well oriented specimens of its potassium salt indicate that the polymer forms a 2-fold helix of pitch 15.

Polysaccharide synthesis in relation to nodulation behavior of Rhizobium leguminosarum.

In this study, we characterized four Tn5 mutants derived from Rhizobium leguminosarum RBL5515 with respect to synthesis and secretion of cellulose fibrils, extracellular polysaccharides (EPS), capsular polysaccharides, and cyclic beta-(1,2)-glucans. One mutant, strain RBL5515 exo-344::Tn5, synthesizes residual amounts of EPS, the repeating unit of which lacks the terminal galactose molecule and the substituents attached to it. On basis of the polysaccharide production pattern of strain RBL5515 exo-344::Tn5, the structural features of the polysaccharides synthesized, and the results of an analysis of the enzyme activities involved, we hypothesize that this strain is affected in a galactose transferase involved in the synthesis of EPS only.

Influence of growth conditions on production of capsular and extracellular polysaccharides by Rhizobium leguminosarum.

The influence of growth rate and medium composition on exopolymer production by Rhizobium leguminosarum was studied. When grown in medium containing 10 g/l mannitol and 1 g/l glutamic acid, Rhizobium leguminosarum biovar trifolii TA-1 synthesized up to 2.0 g/l of extracellular polysaccharide (EPS), and up to 1.

Synthesis of cyclic beta-(1,2)-glucans by Rhizobium leguminosarum biovar trifolii TA-1: factors influencing excretion.

The synthesis of cyclic beta-(1,2)-glucans from UDP-[14C]glucose by a crude membrane preparation and whole cells of Rhizobium leguminosarum bv. trifolii TA-1 was investigated. The crude membrane system needed Mn2+, ATP, and NAD+ for optimal activity.

Levels of trehalose and glycogen in Arthrobacter globiformis under conditions of nutrient starvation and osmotic stress.

Cells of Arthrobacter globiformis grown in carbohydrate-rich media were found to contain large quantities of low-Mr carbohydrates (800 micrograms/mg protein) and only small amounts of amino acids, in addition to high amounts of glycogen (2 mg/mg protein). At increasing osmotic values of the medium, low-Mr carbohydrate levels increased to 1300 micrograms/mg protein. Low-Mr pools were extracted from the cells with hot 75% ethanol, and subjected to thin layer, gel and gas-liquid chromatography.