MOLECULAR-ORGANIZATION OF THE OUTER MEMBRANE OF SALMONELLA-TYPHIMURIUM

Analysis of whole cells of Salmonella typhimurium wild type and of various lipopolysaccharide mutants for their molar lipopolysaccharide content per mg dry weight revealed increasing lipopolysaccharide concentrations concomitant with the degree of lipopolysaccharide sugar deficiency. Cell walls were prepared from all strains by mechanical breakage of cells in the presence of 0.4% sodium dodecylsulfate. The use of the detergent for selective removal of cytoplasmic membrane was justified since it was shown that only minor amounts of lipopolysaccharide were extracted from whole cells during sodium dodecylsulfate treatment. Cell walls were analyzed for peptidoglycan, lipopolysaccharide, phospholipids, proteins and lipoprotein covalently linked to peptidoglycan. The results obtained on a molar basis indicate strongly that rough mutants incorporated increasing amounts of lipopolysaccharide into their cell walls. At the same time, the protein composition changed in some of the mutants. In cell walls of deep rough mutants the lipopolysaccharide concentration increased to about four times that found in the wild type, accompanied by increasing amounts of phospholipids, whereas the protein content decreased. Based on these findings different molecular organizations of the outer membrane in the various strains are discussed. Copyright © 1979, Wiley Blackwell. All rights reserved