Structural Peculiarities and Biological Properties of the Lipopolysaccharide from Herbaspirillum seropedicae Z78

Abstract

Lipopolysaccharide was isolated by phenol extraction from the surface membrane of the nitrogen-fixing endophytic rhizobacterium Herbaspirillum seropedicae, strain Z78. The lipopolysaccharide’s lipid A contained 3-hydroxydecanoic, 3-hydroxydodecanoic, dodecanoic, tetradecanoic, and hexadecanoic acids. The 3-hydroxydodecanoic acid was amide-linked to the sugar backbone of the lipid A. The structure of the O-polysaccharide from H. seropedicae Z78 was established for the first time. It is characterized by heterogeneity and by the presence of glycerol, a component rarely found in gram-negative bacteria. The O polysaccharide of H. seropedicae Z78 was found to consist of two types of repeating units: one represented by glycerol-1-phosphate and the other by the glycerol-1-phosphate of the backbone, which is substituted at the 2-position by N-acetyl-D-glucosamine. The lipopolysaccharide of the H. seropedicae Z78 was weakly toxic to warm-blooded animals and moderately and dose-dependently induced interleukin synthesis by human whole blood cells and NO synthesis by mouse splenocytes. This may indicate that the H. seropedicae lipopolysaccharide is a promising antagonist of classical endotoxins.