Three-dimensional Reconstruction of the Surface Protein of the Extremely Thermophilic Archaebacterium Archaeoglobus fulgidus

The three-dimensional structure of the regular cell surface of Archaeoglobus fulgidus has been determined to a resolution of 1.8 nm. Envelopes prepared by freezing and thawing the cells were treated for 2 sec with 0.01% SDS to ensure optimal negative staining of the cell surface morphological units, which are arranged on an hexagonal lattice with a center to center spacing of 17.5 nm. The three-dimensional structure reveals the morphological unit to be dome-shaped with a wide opening to the cell membrane and a narrow opening to the exterior at the apex. This design principle is reminiscent of H. volcanii and, to a lesser extent of Sulfolobus solfataricus. The morphological units show little evidence of connectivity and the integrity of the lattice appears to rely on the interaction with the cell membrane.