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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.