An improved rapid method for the preparation of D-rhamnose.

A method is developed for the preparation of D-rhamnose from an O-polysaccharide (OPS) isolated by mild acid hydrolysis of Azospirillum brasilense SR75 cell mass. After the OPS hydrolysis, D-rhamnose was recovered by gel-permeation chromatography on Toyopearl TSK HW-40 and was crystallized. The sugar activity was demonstrated immunochemically. The advantages of the method are that it expedites and simplifies the extraction of D-rhamnose and increases its yield.

Structural and functional peculiarities of the lipopolysaccharide of Azospirillum brasilense SR55, isolated from the roots of Triticum durum.

Azospirillum brasilense SR55, isolated from the rhizosphere of Triticum durum, was classified as serogroup II on the basis of serological tests. Such serogroup affiliation is uncharacteristic of wheat-associated Azospirillum species. The lipid A of A. brasilense SR55 lipopolysaccharide contained 3-hydroxytetradecanoic, 3-hydroxyhexadecanoic, hexadecanoic and octadecenoic fatty acids. The structure of the lipopolysaccharide's O polysaccharide was established, with the branched octasaccharide repeating unit being represented by l-rhamnose, l-3-O-Me-rhamnose, d-galactose and d-glucuronic acid. The SR55 lipopolysaccharide induced deformations of wheat root hairs. The lipopolysaccharide was not involved in bacterial cell aggregation, but its use to pretreat wheat roots was conducive to cell adsorption. This study shows that Azospirillum bacteria can utilise their own lipopolysaccharide as a carbon source, which may give them an advantage in competitive natural environments.