Structure of the Oligosaccharide Chain of the SR-Type Lipopolysaccharide of Ralstonia solanacearum Toudk-2

摘要

Aiming at improving classification and taxonomy of Gram-negative phytopathogenic bacteria,we studied the structure of the lipopolysaccharide of Ralstonia solanacearum.Mild acid hydrolysis of the lipopolysaccharide of strain Toudk-2 followed by gel chromatography resulted in an O-polysaccharide and two oligosaccharide fractions.The smallest-size oligosaccharide fraction was studied by sugar analysis,high-resolution electrospray ionization mass spectrometry,and,after fractionation by anion-exchange chromatography on HiTrap Q,by one-and two-dimensional ~1H and ~(13)C NMR spectroscopy.It was found that the isolated oligosaccharides consist of the lipopolysaccharide core with one O-polysaccharide repeat(O-unit)attached.The core exists in two major glycoforms differing from each other in a lateral octulosonic acid residue,which is either D-glycero-D-talo-oct-2-ulosonic acid or 3-deoxy-D-manno-oct-2-ulosonic acid.A peculiar feature of the core is the occurrence of 4-amino-4-deoxy-L-arabinose nonstoichiometrically linked to a heptose residue.The full structures of the core and the biological O-unit as well as the site of the attachment of the O-unit to the core were established.