Determination of Keto-deoxy-d-manno-8-octanoic acid (KDO) from Lipopolysaccharide of Escherichia coli

Abstract

2-Keto-3-deoxy-octonate (KDO) IS an essential constituent of lipopolysaccharide (LPS) that forms the outermost leaflet of Gramnegative ba([erial outer membrane. LPS is mainly composed of lipid A. 0 -antigen and a core oligosaccharide. Two molecules of KDO are present per one molecule of LPS. A proper level of LPS is required to maintain the outer membrane Integrity and either high or low levels of LPS are COXIC to the cell. Various methods are available for quantification of LPS; of these, determination of KDO is a simple and accurate method and it can be estimated either directly from crude bacterial cell lysates or from purified LPS by a simple colorimetric assay. Although this procedure can be theoretically used for any Gram-negative bacterium, we used it routinely to measure KDO from celllysa tes of Escf1ericl7ia coli(E. colt) K12 strains.