Structure of the Lipopolysaccharide Core Region

Most Gram-negative bacteria (exceptions are Treponema pallidum, Borrelia burgdorferi and B. hispanica, Sphingomonas capsulata and S. paucimobili, Thermus thermophilus, and Meiothermus taiwanensis [1–7]) contain lipopolysaccharide (LPS) in their outer membrane [8]. In general, the LPS may be present either in the smooth form (S, possessing the polysaccharide region) or in the rough form (R, lacking the polysaccharide, also called lipooligosaccharide, LOS). Both forms contain lipid A [9] and a core oligosaccharide (OS) that comprises up to 15 sugar residues [8–17].