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 0-specific polysaccharide side chains but do have a complete core region.2. R forms of Citrobacter 010,9b and Arizona 09a,9c were isolated a t 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 R l 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. I n serological studies lipopolysaccharides of all R types except coli R l were found to cross react with each other, thus indicating structural similarities. I n au cross reacting lipopolysaccharide preparations the same sugar constituents namely glucose, galactose, N-acetylglucosamine, L-glycero-D-manno-heptose and 3-deoxy-~-mannooctulosonic 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.According to numerous investigations [l, 21 the Salmonella cell wall lipopolysaccharides (0-antigens) are composed of three different structural regions : the 0-specific side chains, the core oligosaccharide and the lipid A (see Fig. 1).The 0-specific chains are built up from repeating oligosaccharide units which vary widely in composition and structure among the different serotypes. I n the smooth (S) strains these chains are bound to a core oligosaccharide having R specificity and which, in turn, is linked via 3-deoxy-~-manno-octu~osonic acid (KDO) units to the third structural entity, the lipid A.It has been shown [3--61 that the synthesis of the 0-specific side chains and of the core oligosaccharide is mainly determined by two independent gene Unmuul Abbreviation. KDO, 3-deoxy-~-manno-octulosonic acid.clusters on the bacterial chromosome, termed rfb and rfa, respectively. The rfa clust...

Aggregating cells of Dictyostelium discoideum form EDTA-stable cell contacts which are blocked by a Fab (antigen-binding fragment) preparation from antisera raised against membranes. The target site of the blocking Fab fragments has been identified as a specific glycoprotein. In this paper its purification, carbohydrate and amino acid composition are described. Purification was 800-fold, starting with cells lysed by digitonin. The plasma membranes, preserved as ghosts by this treatment, were purified in a two-phase system and extracted with butan-1-01. The water phase contained predominantly concanavalin-A-binding glycoproteins and was particularly rich in contact sites A. These were further purified on DE-cellulose and sucrose gradients. Sodium dodecylsulphate/polyacrylamide gel electrophoresis of the purified material revealed one major glycoprotein band in the molecular weight region of 80000 to 90000, depending on the acrylamide concentration. The sugars found in contact sites A were mannose, N-acetylglucosamine, fucose, and possibly glucose. The protein moiety contained 8 % proline and was particularly rich in hydroxy amino acids.

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For the first time, an 0-antigenic lipopolysaccharide (LPS) has been isolated from a filamentous blue-green alga (Anabaena variabilis). It was extractable with phenol-water, resulting in extraction of the bulk of the LPS into the phenol phase. The polysaccharide moiety of this LPS consists of L-rhamnose, its 3-0-methyl ether L-acofriose, D-mannose, D-glucose, and D-galactose. L-Glycero-D-mannoheptose and 2-keto-3-deoxyoctonate, the two characteristic sugar components of enteric LPS, and phosphate groups are absent from the A. variabilis O antigen. The only amino sugar present is D-glucosamine. Three hydroxy fatty acids were identified, namely, ,-hydroxymyristic, ,-hydroxypalmitic and B-hydroxystearic acids, in addition to palmitic and unidentified fatty acid. The LPS of A. variabilis is localized in the outermost cell wall layer and behaves like a bacterial 0 antigen in serological tests. The passive hemagglutination yielded high titers with isolated LPS (pretreated by heat or by alkali) and rabbit antisera prepared against living or heat-killed cells. The position of the precipitation arcs after immunoelectrophoresis of the 0 antigen indicates the lack of charged groups. The water phase of the phenol-water extract contains, in high yield, a glucose polymer. It is serologically inactive as shown by the passive hemagglutination test and by agar-gel precipitation.