Sulfolobus cells   

This transmission electron micrograph shows an ultrathin section of several S. acidocaldarius cells (diameter of each is about 1 micrometer).  The unusual structure of the Sulfolobus cell envelope is clearly visible around the margins of the cells. The envelope consists of a layer of a porous glycoprotein layer held out from the cell membrane a distance of about 15 nm.  The regular repeating structure of the glycoprotein complex can be seen in the lower left, where the section follows the plane of this layer.  For alternative views of these structures, see negative-stained images.