Cytoskeletal origins in sulfur-metabolizing archaebacteria.

Several of the thermophilic acidopholic sulfur-metabolizing archaebacteria lack rigid cell walls. Their irregular shapes were maintained by an internal mechanism, presumably a cytoskeleton. Apparently this is an adaptation for respiration upon elemental sulfur, which requires cell contact since sulfur is insoluble in water. Also, we speculate that there could be additional functions of the cytoskeleton, such as prevention of osmotic cell lysis, thermal stabilization of enzymes, and improvements in metabolic efficiency through specific enzyme positioning. Such a well-developed cytoskeleton, evolving first in thermophilic archaebacteria, could have been a preadaptation for the evolution of eukaryotic cells.