Archaea differ from Bacteria primarily in membrane biochemistry containing isoprenoid chains ether-linked to glycerol-1-phosphate backbone forming diether archaeol or tetraether caldarchaeol monolayers, contrasting ester-linked fatty acids to glycerol-3-phosphate in Bacteria and Eukarya. Ether linkages confer thermal stability, proton impermeability, and resistance supporting extremophilic lifestyles in hot springs and acidic environments. Additional distinguishing features include absence of typical peptidoglycan, presence of pseudomurein or protein S-layer, unique RNA polymerase complexity,
Ref:
Alberts Molecular Biology Cell 6th ed., Archaeal membrane ether lipids; Brock Biology Microorganisms 15th ed., Archaea membranes archaeol