Biomaterial Database

Freeze-etching and x-ray diffraction of the isolated double-track layer from the cell wall of a gram-negative marine pseudomonad. 1973

A Forge, and J W Costerton, and K A Kerr

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.

UI	MeSH Term	Description	Entries
D008386	Marine Biology	The study of the origin, structure, development, growth, function, genetics, and reproduction of organisms which inhabit the OCEANS AND SEAS.	Biology, Marine,Marine Ecology,Marine Hydrobiology,Ecology, Marine,Hydrobiology, Marine
D008854	Microscopy, Electron	Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.	Electron Microscopy
D011549	Pseudomonas	A genus of gram-negative, aerobic, rod-shaped bacteria widely distributed in nature. Some species are pathogenic for humans, animals, and plants.	Chryseomonas,Pseudomona,Flavimonas
D002473	Cell Wall	The outermost layer of a cell in most PLANTS; BACTERIA; FUNGI; and ALGAE. The cell wall is usually a rigid structure that lies external to the CELL MEMBRANE, and provides a protective barrier against physical or chemical agents.	Cell Walls,Wall, Cell,Walls, Cell
D005613	Freeze Etching	A replica technique in which cells are frozen to a very low temperature and cracked with a knife blade to expose the interior surfaces of the cells or cell membranes. The cracked cell surfaces are then freeze-dried to expose their constituents. The surfaces are now ready for shadowing to be viewed using an electron microscope. This method differs from freeze-fracturing in that no cryoprotectant is used and, thus, allows for the sublimation of water during the freeze-drying process to etch the surfaces.	Etching, Freeze
D001419	Bacteria	One of the three domains of life (the others being Eukarya and ARCHAEA), also called Eubacteria. They are unicellular prokaryotic microorganisms which generally possess rigid cell walls, multiply by cell division, and exhibit three principal forms: round or coccal, rodlike or bacillary, and spiral or spirochetal. Bacteria can be classified by their response to OXYGEN: aerobic, anaerobic, or facultatively anaerobic; by the mode by which they obtain their energy: chemotrophy (via chemical reaction) or PHOTOTROPHY (via light reaction); for chemotrophs by their source of chemical energy: CHEMOLITHOTROPHY (from inorganic compounds) or chemoorganotrophy (from organic compounds); and by their source for CARBON; NITROGEN; etc.; HETEROTROPHY (from organic sources) or AUTOTROPHY (from CARBON DIOXIDE). They can also be classified by whether or not they stain (based on the structure of their CELL WALLS) with CRYSTAL VIOLET dye: gram-negative or gram-positive.	Eubacteria
D012623	Seawater	The salinated water of OCEANS AND SEAS that provides habitat for marine organisms.	Sea Water,Sea Waters,Seawaters,Water, Sea,Waters, Sea
D013194	Staining and Labeling	The marking of biological material with a dye or other reagent for the purpose of identifying and quantitating components of tissues, cells or their extracts.	Histological Labeling,Staining,Histological Labelings,Labeling and Staining,Labeling, Histological,Labelings, Histological,Stainings
D014871	Water Microbiology	The presence of bacteria, viruses, and fungi in water. This term is not restricted to pathogenic organisms.	Microbiology, Water
D014961	X-Ray Diffraction	The scattering of x-rays by matter, especially crystals, with accompanying variation in intensity due to interference effects. Analysis of the crystal structure of materials is performed by passing x-rays through them and registering the diffraction image of the rays (CRYSTALLOGRAPHY, X-RAY). (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	Xray Diffraction,Diffraction, X-Ray,Diffraction, Xray,Diffractions, X-Ray,Diffractions, Xray,X Ray Diffraction,X-Ray Diffractions,Xray Diffractions