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Salmonella minnesota R 595 (Re) and other Salmonella strains incorporate cis-delta 9-16:1 (palmitoleic acid) at the expense of mainly dodecanoic acid into the lipid-A portion of lipopolysaccharides, when the cells are grown at low temperature (12 degrees C). It has recently been shown, that in S. minnesota R 595 grown at 37 degrees C dodecanoic acid is linked to the 3-hydroxyl group of an amide-bound 3-hydroxytetradecanoic acid. The present data suggest, that cis-delta 9-16:1 occupies the same position in lipid A (12 degrees C).

Structural investigations have shown that lipid A constitutes the active principle of lipopoly saccharide (LPS, endotoxin), a complex amphipathic molecule located on the cell surface of Gram-negative bacteria.1 Lipid A elicits not only the typical endotoxic reactions such as fever and lethal shock but also adjuvant, antitumor and other beneficial effects.1 As a result, there has been a great deal of interest in the synthesis of lipid A derivatives possessing low toxicity.1,2

Lipid A preparations from the lipopolysaccharides of four Salmonella minnesota R mutants and one Escherichia coli 0100 R mutant were assayed as soluble complexes with bovine serum albumin for lethality in mice, pyrogenicity in rabbits and complement inactivation. Although generally less active than endotoxic lipopolysaccharides, these lipid · albumin complexes nevertheless exhibited strong biological activity. These results indicate that lipid A contains the endotoxic principle of bacterial lipopolysaccharides.

Based on chemical alterations in the cell surface of normal cells following transformation and the fixation of bacterial glycolipid mR595 by normal, transformed and trypsinized cells, theoretical models for the insertion of glycolipid mR595 in the lipid bilayer of normal, trypsinized and transformed cells are presented.

About 30 R mutants derived from Salmonella minnesota and Salmonella ruiru and the corresponding wild-type strains were analysed comparatively for the presence of enzymes catalyzing the synthesis of UDP-glucose, UDP-galactose, UDP-N-acetylglucosamine and UDP-N-acetylgalactosamine.