Structural and Conformational Study of the O-Antigenic Portion of the Lipopolysaccharide Isolated from Burkholderia gladioli pv. cocovenenans

Abstract

Lipopolysaccharides (LPSs) are virulence factors that are expressed on the cell surface of Gram-negative bacteria. They represent one of the main traits of bacterial virulence. In this paper, we report the primary structure and the conformational features of the O-chain from the lipopolysaccharide (LPS) produced by Burkholderia gladioli pv. cocovenenans, a bacterium often associated with the mucoralean fungus Rhizopus microsporus var. oligosporus, which is traditionally used in food fermentations. With the aim of understanding the organization of bacterial cell-surface components, we isolated and characterized the following O-antigenic portions of the LPS from B. gladioli pv. cocovenenans: [2)--Rha-(12)--Aco-(12)--Rha-(14)--Gal2Me-(1]_n and [2)--Rha-(12)--Aco-(12)--Rha-(14)--Gal-(1]_n. A distinctive feature of the O-chain is the presence of methylated sugar residues. This contributes to the creation of a hydrophobic shield. The experimental data were confirmed by conformational studies, which showed three-dimensional shapes with different packings and extensions. Such features determine the physicochemical properties of the bacterial envelope, and might contribute to the ability to adapt the membrane surface to the host.

B. gladioli pv. cocovenenas is a plant-pathogenic bacterium isolated from mucoralean fungus Rhizopus microsporus var. oligosporus. We have determined the structure and spatial arrangement of the O-polysaccharide portions of the lipopolysaccharide.

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