ABSTRACT
Depending on the size of the saccharide portion, there exist two types of lipopolysaccharides (LPS), i.e., smooth- and rough-form (S- and R-form) LPS (1–3). Both consist of lipid A and, covalently linked to it, a saccharide portion composed of up to 15 sugars—the core region (3–5). In S-form LPS, this core region is replaced by the O-specific polysaccharide. Both LPS forms are found in wild-type gram-negative bacteria: the S-form, for example, in Escherichia coli, Klebsiella pneumoniae, Acinetobacter, or Vibrio cholerae, and the R-form in Neisseria meningitidis, N. gonorrhoeae, Haemophilus influenzae, and Bordetella pertussis. Mutants that are not able to synthesize a minimal core structure are not viable. Thus, the core region and lipid A represent a common structural unit occurring in all LPS, suggesting these components to be important for viability and membrane function. Herein, the chemical structure of the core regions of LPS is reviewed. Although part of the work was summarized recently (3–5), this review contains all structures presently known and the respective references.
