ASSOCIATION OF PLASMIDS WITH THE CARBOHYDRATE-COMPOSITION OF THE O-ANTIGEN IN SHIGELLA-DYSENTERIAE TYPE-1

Six different prepared mutant strains of Shigella dysenteriae type 1 w ith various combination of 'core' plasmids of 140, 6, and 2 Mdal, were cultivated separately and their lipopolysaccharide (LPS) samples were isolated, which on delipidation afforded polysaccharides and oligosac charides. The LPS and prepared O-antigen polysaccharides were subjecte d to acid hydrolysis, and the constituent sugars were analysed by pape r chromatography and gas liquid chromatography (GLC), using CP Sil 8 C B fused silica capillary column equipped with a flame ionization detec tor. The mutant strains, harbouring the 6 Mdal plasmid, contained rham nose, galactose, and N-acetyl glucosamine in their O-antigen polysacch arides with a minor variation in the relative proportions of these sug ar constituents as compared to those of the control strain. The sugar composition of the O-antigen polysaccharides prepared from the mutant strains, without the 6 Mdal plasmid but containing 2 or 140 Mdal plasm id, contained galactose and N-acetyl glucosamine but no rhamnose. Howe ver, mutant strains with none of the core plasmids contained traces of rhamnose and were devoid of N-acetyl glucosamine, but contained hepto se. These results suggest that 6 Mdal plasmid is essentially required for the complete synthesis of O-antigen polysaccharides. However, the 140 and 2 Mdal plasmids might also have an association with synthesis of carbohydrate, composition of the O-antigen in S. dysenteriae type 1 .