title: Freeze-etching and x-ray diffraction of the isolated double-track layer from the cell wall of a gram-negative marine pseudomonad.
abstract: The isolated double-track layer of the cell wall of the gram-negative marine pseudomonad studied here contains a cleavage plane. This finding localizes the single cleavage plane of the cell wall and shows that the molecular architecture of this layer provides the lipid-enriched layer which cleaves preferentially in the frozen cell. The observation that the isolated double-track layer of the cell wall is sufficiently ordered at the molecular level to yield a well-defined X-ray diffraction pattern with a d-spacing of 0.44 nm shows that its molecular architecture is very similar to that of true membranes. This specific d-spacing is produced by the highly ordered packing of the hydrophobic portions of phospholipid molecules. Therefore, the double-track layer of the cell wall has been shown, by these two biophysical means, to have a molecular architecture which would allow it to function as the membrane-like "molecular sieve" layer, whose presence has been deduced from physiological data. This layer is important in the retention of cell wall-associated enzymes and in the control of the movement of large molecules through the cell wall.
mesh_terms: D001419:Bacteria / Q000166:cytology; D002473:Cell Wall / Q000502:physiology; D005613:Freeze Etching; D008386:Marine Biology; D008854:Microscopy, Electron; D011549:Pseudomonas / Q000166:cytology*; D012623:Seawater; D013194:Staining and Labeling; D014871:Water Microbiology; D014961:X-Ray Diffraction