Characterization of the ultrastructure and the self-assembly of the surface layer of Bacillus stearothermophilus strain NRS 2004/3a.
The ultrastructure of the crystalline surface layer (S-layer) of Bacillus stearothermophilus strain NRS 2004/3a has been characterized by electron microscopy supplemented by optical and computer image analysis. The S-layer, composed of glycoprotein subunits, has oblique symmetry, and can be extracted by guanidine hydrochloride. Upon dialysis, this extract produced both flat and cylindrical mono- and double-layer self-assembly products. Optical diffraction analysis of negatively stained preparations showed five types of double-layered assembly products. Computer filtering separated the double-layer complexes and revealed them to be composed of a common monolayer with p2-symmetry (a = 9.4 nm, b = 11.6 nm, and gamma = ca. 78 degrees). By analysis of freeze-dried and heavy metal-shadowed self-assemblies the surface topography and the characteristic "handedness" of the morphological units have been determined. Labeling with polycationic ferritin has shown that each surface of the S-layer possessed a different net charge. The results indicate that S-layers in vivo could prevent autoagglutination of cells.
Messner
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P
Zentrum für Ultrastrukturforschung, Universität für Bodenkultur, Wien, Austria.
Pum
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D
Sleytr
U B
UB
D002462:Cell Membrane / Q000648:ultrastructure; D005613:Freeze Etching; D001411:Geobacillus stearothermophilus / Q000648:ultrastructure*; D008562:Membrane Glycoproteins / Q000032:analysis*; D008854:Microscopy, Electron
D008562:Membrane Glycoproteins