ABSTRACT
Gallia omnia divisa est in partes tres (all gallia are divided into three parts) was written almost 2000 years ago by the Roman Caesar about a part of the world that has since become better known as France. Likewise, in 1978, Woese and his coworkers divided the whole formerly dualistic world of prokaryotic and eukaryotic cells into three parts: eukaryotes, bacteria, and the new kingdom of archaea (singular: archaeon). I do not want to go into phylogenetic criteria of each of the three kingdoms; however, one characteristic issue that separates archaea from all other cells must be referred to in this context: phytanol ether lipids. In archaeal membranes, we find various types of diether and tetraether lipids, differently interdigitated or even covalently omega-linked. The latter case results in tetraether lipids with one or two membrane-spanning biphytanyl chains.
