title: Asymmetrical distribution and artifactual reorientation of lipopolysaccharide in the outer membrane bilayer of Salmonella typhimurium.
abstract: Labelling of cell walls or outer membranes from Salmonella typhimurium with ferritin-conjugated antibodies directed against the polysaccharide moiety of the lipopolysaccharide gave the following results: 1. Cell walls or outer membranes from which the mucopeptide had been removed by lysozyme digestion at 0 degrees C carried the label on the outer face of the membrane. 2. When the murein layer was removed by either lysozyme or trypsin at physiological temperature (25-37 degrees C) subsequent labelling showed the lipopolysaccharide to be present on both membrane faces. 3. This reorientation could be achieved by a 1-min treatment of the membranes at 37 degrees C. 4. Glutaraldehyde fixation of the outer membranes did not entirely prevent but somewhat inhibited the temperature-induced reorientation process. 5. The same reorientation phenomenon was observed in lysozyme spheroplasts, which were prepared at 37 degrees C and were subsequently lysed in hypotonic medium at 0 degrees C. These observations are discussed as evidence for a transmembrane movement of lipopolysaccharide, which only takes place in areas where the mucopeptide layer is defective, and only when the temperature is sufficiently high to allow such movement.
mesh_terms: D000937:Antigen-Antibody Reactions; D001692:Biological Transport; D002462:Cell Membrane / Q000032:analysis / Q000648:ultrastructure; D002473:Cell Wall / Q000032:analysis / Q000648:ultrastructure; D005293:Ferritins; D005976:Glutaral; D008070:Lipopolysaccharides / Q000032:analysis* / Q000276:immunology / Q000378:metabolism; D008854:Microscopy, Electron; D009113:Muramidase; D011135:Polysaccharides, Bacterial / Q000032:analysis* / Q000276:immunology / Q000378:metabolism; D012486:Salmonella typhimurium / Q000032:analysis / Q000378:metabolism / Q000648:ultrastructure*; D013104:Spheroplasts / Q000032:analysis / Q000648:ultrastructure; D013696:Temperature; D013997:Time Factors; D014357:Trypsin
chemical_list: D008070:Lipopolysaccharides; D011135:Polysaccharides, Bacterial; D005293:Ferritins; D009113:Muramidase; D014357:Trypsin; D005976:Glutaral