Immunochemical Studies on Core Lipopolysaccharides of Enterobacteriaceae of Different Genera

1 R forms of Escherichia coli 0100:K(B) and 0111:K58 were obtained by genetic recombination transferring into the respective S forms a lesion in the his‐linked som locus. Such mutants are not able to synthesize O‐specific polysaccharide side chains but do have a complete core region. 2 R forms of Citrobacter 010,9b and Arizona 09a,9c were isolated at random as rough looking colonies and characterized as possessing complete core lipopolysaccharide. 3 These R forms and their respective lipopolysaccharides were compared in phage sensitivity, serological properties and in chemical composition with known prototypes of Salmonella and E. coli R mutants (coli R1 and R2) having a complete core structure. 4 According to the phage pattern, the R mutants could be subdivided into distinct groups. One group comprising the R forms of E. coli 0111 and Citrobacter showed a peculiar phage pattern hitherto not observed with other enterobacterial R mutants. The phage pattern of R mutants of Salmonella and Arizona proved to be identical. The R form of E. coli 0100 on the other hand gave the same phage pattern as described for E. coli R2 type mutants. 5 The results of phage typing were fully corroborated by the serological and chemical investigations upon the lipopolysaccharide. In serological studies lipopolysaccharides of all R types except coli R1 were found to cross react with each other, thus indicating structural similarities. In all cross reacting lipopolysaccharide preparations the same sugar constituents namely glucose, galactose, N‐acetylglucosamine, l‐glycero‐d‐manno‐heptose and 3‐deoxy‐d‐manno‐octulosonic acid were present; but quantitative analysis revealed remarkable differences. Striking is the very low content of galactose in the lipopolysaccharide of the R mutants of E. coli 0111 and Citrobacter. 6 The results described show that the E. coli 0111 core represents a further core type which will be designated coli R3. 7 The serological and chemical investigation of the lipopolysaccharide of the Arizona R mutant confirms its identity with the Salmonella core type, thus indicating the close relationship of these bacterial groups.