Immunochemical Studies on Lipopolysaccharides from Wild‐Type and Mutants of Escherichia coli K‐12

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Abstract
Lipopolysaccharides from E. coli K-12 mutants were investigated by chemical and serological methods. Passive hemagglutination inhibition and precipitation inhibition show that L-rhamnose is the immunodominant sugar in the lipopolysaccharide from wild-type E. coli K-12. The disaccharide rhamnosyl-KDO [3-deoxy-D-manno-octulosonic acid] was isolated and characterized after mild acid hydrolysis of the lipopolysaccharide. The rhamnose is apparently present in the innermost part of the core as a side-chain substituent on KDO. From crosses between an E. coli K-12 donor and E. coli O 8, hybrids were obtained which contained 1 or both of the donor rfa and rfb clusters. Serum absorption studies with lipopolysaccharides from these hybrids indicated that the histidine-linked rfb cluster is responsible for the presence of rhamnose in the K-12 core oligosaccharide. Using paper chromatography of 32-labeled lipopolysaccharides, heterogeneous lipopolysaccharide in 2 strains and some differences between 2 wild-type strains were found. The latter difference believed to be due to varying contents of KDO-linked ethanolamine phosphate. These and other results clearly show that the core oligosaccharide of E. coli K-12 has a structure different from other strains of E. coli (designed coli R1 to coli R4).