Isolation and fractionation of cell envelope from the extreme thermo-acidophile Sulfolobus acidocaldarius

Methods to produce membrane fragments of defined composition were evaluated for their applicability to the extremely thermophilic, acidophilic archaeon Sulfolobus acidocaldarius. Sonication was found to effectively disrupt Sulfolobus cells and to produce small vesicles of varying size. Alternatively, grinding cells with fine alumina yielded large, uniform vesicles retaining the characteristic cell envelope ultrastructure of Sulfolobus spp. Biochemical and electron-microscopic examination indicated that the 'cell ghosts' prepared from S. acidocaldarius by the latter method have a relatively simple protein composition dominated by the glycoprotein subunits of the organism's quasicrystalline surface (S) layer cell wall. By suitable treatments, the cell ghosts could, in turn, be used to prepare S layer without the associated lipid membrane, or conversely, to prepare cytoplasmic membrane lacking the apposed S layer. These results offer a basis for compositional and functional analyses of a cell surface that is normally exposed to extremely severe environmental conditions.