title: Characterization of the ultrastructure and the self-assembly of the surface layer of Bacillus stearothermophilus strain NRS 2004/3a.
abstract: 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.
authors.affiliation: Zentrum für Ultrastrukturforschung, Universität für Bodenkultur, Wien, Austria.
authors.forename: P
authors.initials: P
authors.lastname: Messner
authors.forename: D
authors.initials: D
authors.lastname: Pum
authors.forename: U B
authors.initials: UB
authors.lastname: Sleytr
mesh_terms: D002462:Cell Membrane / Q000648:ultrastructure; D005613:Freeze Etching; D001411:Geobacillus stearothermophilus / Q000648:ultrastructure*; D008562:Membrane Glycoproteins / Q000032:analysis*; D008854:Microscopy, Electron
chemical_list: D008562:Membrane Glycoproteins