Morphological Model of the Surface-Layer Array in Spirillum serpens

Abstract

The presence of an extensive, periodic surface-layer structure on the gram-negative bacterium Spirillum serpens VHA was first reported by Murray (1963). Murray and collaborators demonstrated that heating the bacteria at 60°C released the periodic surface layer material from the cell wall, and that this released material could be readily isolated by differential centrifugation. Subsequent work established that the surface layer structure is composed of a Single polypeptide, whose apparent molecular weight is ~ 140,000 (Buckmire and Murray, 1973; Glaeser et al., 1979). This protein is attached to the external surface of the outer membrane, called the “backing layer” by Murray and collaborators. Murray has demonstrated that the crystalline surface-layer protein can be removed by treatment with 1.5M guannidine HCl, and that reconstitution onto the naked outer membrane material is facilitated by calcium ions (Buckmire and Murray, 1973,1976; ehester and Murray, 1978). The outer membrane itself is composed of lipopolysaccarides and phospholipids (Buckmire and Murray, 1973; ehester and Murray, 1975,1978) and of at least two major polypeptides having apparent molecular weights of ~35,000 and ~78,000 (Glaeser et al., 1979).