Gram-negative rod shaped bacterium Myxococcus xanthus DK1622 produces a smooth-type LPS. The structure of the polysaccharide O-chain and the core-lipid A region of the LPS has been determined by chemical and spectroscopic methods. The O-chain was built up of disaccharide repeating units having the following structure:→6)-α-d-Glcp-(1→4)-α-d-GalpNAc6OMe∗-(1→with partially methylated GalNAc residue. The core region consisted of a phosphorylated hexasaccharide, containing one Kdo residue, unsubstituted at O-4, and no heptose residues. The lipid A component consisted of β-GlcN-(1→6)-α-GlcN1P disaccharide, N-acylated with 13-methyl-C14-3OH (iso-C15-3OH), C16-3OH, and 15-methyl-C16-3OH (iso-C17-3OH) acids. The lipid portion contained O-linked iso-C16 acid.