Superficial cell-wall layers on Spirillum "Ordal" and their in vitro reassembly

Abstract

The cell envelope of Spirillum sp. strain "Ordal" (possibly a variety of S. anulus) demonstrated multiple superficial wall layers which were diverse in their macromolecular arrays. Negative staining and freeze-etching techniques revealed an outer hexagonally packed layer and an inner tetragonally packed layer. However, both thin sections and freeze-etched cleavages of the wall showed that each of these regular structures rested upon a backing layer, and that there was a delicate amorphous layer overlying the outer hexagonal array. Rotary integration, optical diffraction, and reconstruction of image were used to clarify measurements of each array and to verify the validity of a diagrammatic model of the outer hexagonal system. The integrity of these layers required suitable cations (Ca2+ appeared essential) and pH ([Formula: see text] dissociated most superficial layers). These observations aided in the development of a low-pH cationic-substitution technique, in which Na+ replaced essential Ca2+, for extraction of the layers from the cell surface. Dialysis to remove Na+ and restoration of Ca2+ initiated in vitro reassembly of the superficial layer components until regularly structured assembly products were formed.