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SUMMARY: Isolated lipopolysaccharide from a rough mutant of Salmonella minnesota was shown to act as a receptor for Felix 0-1 bacteriophage. The isolated receptor structure could be dissociated by sodium deoxycholate with subsequent loss of receptor activity. When the deoxycholate was removed by dialysis the receptor activity was restored. Ultrasonic treatment destroyed the receptor activity and electron micrographs indicated that the ultrasonic treatment had altered the structure of the lipopolysaccharide. The experiments suggest that the inactivation of phages can be used as a test of the biological activity of a lipopolysaccharide. The interaction between the 0-1 phage and the receptor structure was also studied with the aid of electron microscopy.

SUMMARY: Envelope proteins of one smooth (S) strain and seven rough (R) mutants of Salmonella minnesota were examined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. All strains gave similar band patterns although some consistent differences were detected. A major polypeptide band at 54k, which coincided with the flagellar component, was more prominent in S, Ra and Rb than in the Rc, Rd and Re chemotypes. The latter strains, however, showed more prominent bands at 48, 19 and 18k. The stage of growth at which the cultures were harvested was also found to affect the band patterns, particularly in the 54 and 40k regions. A closer examination of S, Ra and Re strains suggested that the levels of the major 40 and 37k bands were slightly reduced in Re. It is concluded that the progressive loss of lipopolysaccharide components which occurs from the S chemo-type through various degrees of roughness to Re is accompanied by a change in the envelope protein composition, apparently between Rb and Rc.

Summary: Homologous and heterologous haemagglutinin responses in rabbits to heat-killed R-mutants of Salmonella minnesota (chemotypes ranging from Ra to Re) were measured throughout the course of immunization. In each case the strongest response was directed against the homologous R-antigen, but in most cases cross-reactions with antigens of heterologous R-chemotypes were detected. Absorption studies with erythrocytes coated with R-lipopolysaccharides indicated that haemagglutinin reactions with homologous and heterologous R-antigens in R-antisera were due to several different populations of antibodies. In general, these populations consisted of: (i) antibodies strictly specific for the homologous antigen; (ii) antibodies reacting with the homologous antigen, but also able to react in varying degrees with heterologous R-lipopolysacharides of more complete chemo-types; (iii) antibodies directed against internal portions of the R-oligosaccharide; and (iv) antibodies strictly specific for a less complete form of the R-oligosaccharide molecule. Characteristic responses were obtained for each of the R-mutants with respect to the presence or absence of any one of the above-mentioned antibody populations in antisera at a given period after immunization.