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Polymxyin treatment of isolated lipopolysaccharide from Escherichia coli resulted in the breakdown of its structure.

The fine structure of lipopolysaccharide (LPS), isolated from an avian strain of Escherichia coli 018, was examined by electron microscopy. In positively stained preparations, ribbonlike structures with frequent branching were observed as previously reported (4). Two densely stained parallel lines were occasionally seen associated with a ribbon. When negative staining was employed, the LPS appeared as a branching ribbon with one central and two lateral zones divided by two relatively dense parallel lines running the complete length of the ribbon. The lateral zones were probably due to the 0-antigenic side chains of the LPS. This interpretation was supported by the fact that the electron microscopic structure of the LPS from two rough strains, E. coli K-12 Gal 23 and Salmonella typhimurium TV1 19 RII, both lacking the 0-specific side chains, did not possess the outer lateral zones.

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Lipopolysaccharide (LPS) was isolated from an avian strain of Escherichia coli O18 by extraction of the cells with NaCl followed by treatment with phenol–water, methanol precipitation, and gel permeation chromatography. The LPS consisted of carbohydrate, lipid, and a small amount of protein and phosphate. Further analysis showed the presence of glucose, galactose, rhamnose, glucosamine, N-acetylglucosamine, heptose, 2-keto-3-deoxyoctonate (KDO), and ethanolamine. The composition of the LPS is qualitatively similar to that found for LPS obtained from various other bacteria.