Structural studies of a neutral polymeric fraction from the lipopolysaccharide of Serratia marcescens C.D.C. 1783-57 (O14:H9).

A "neutral" polymer of glucose, galactose, and 2-acetamido-2-deoxyglucose (molar ratios 1:1:2) has been isolated from the lipopolysaccharide of Serratia marcescens strain C.D.C. 1783-57 (O14:H9). Degradative and spectroscopic studies established that the polysaccharide has a branched tetrasaccharide repeating-unit of the structure shown. The polymer was absent from other strains of serogroup O14 studied, but a polymer differing only in the configuration of the glucose residue has previously been isolated from a strain of S. marcescens O8. The polymer from strain C.D.C. 1783-57 also shares structural features with the Escherichia coli O18 antigen, which is known to be serologically related to the S. marcescens O8 antigen. (Formula: see text).