Osmoregulated periplasmic glucans of Erwinia chrysanthemi

We report the initial characterization of the osmoregulated periplasmic glu cans (OPGs) of Erwinia santhemal. OPGs are intrinsic components of the bact erial envelope necessary to the pathogenicity of this phytopathogenic enter obacterium. OPGs were isolated by trichloracetic acid treatment and gel per meation chromatography. The synthesis of these compounds appeared to be osm oregulated, since lower amounts of OPGs were produced when bacteria were gr own in media of higher osmolarities. However, a large fraction of these OPG s were recovered in the culture medium. Then, these compounds were characte rized by compositional analysis, high-performance anion-exchange chromatogr aphy, matrix-assisted laser desorption mass spectrometry, and H-1 and C-13 nuclear magnetic resonance analyses. OPGs produced by E. chrysanthemi are v ery heterogeneous at the level of both backbone structure and substitution of these structures. The degree of polymerization of the glucose units rang es from 5 to 12. The structures are branched, with a linear backbone consis ting of beta -1,2-linked glucose units to which a variable number of branch es, composed of one glucose residue, are attached by beta -1,6 linkages in a random may. This glucan backbone may be substituted by O-acetyl and O-suc cinyl ester-linked residues.