Role of membrane lipids in the first specific differentiation

1. Abstract. All the living organisms are classified into three domains (the newly proposed highest rank of classification of organisms). Escherichia coli and Bacillus subtilis are belonging to one of the domains, Bacteria. Works on the two bacteria made a great deal of contribution to construct modern microbiology, new concept of biochemistry and molecular biology. Compared with research history on Bacteria, Archaea have been studied merely in these three decades, however, the uniformity and diversity in biochemical properties of Archaea seem to illustrate pre-existing knowledge of Bacteria from the back, that is, bacterial information that had been ignored was discovered as novel aspects of biochemistry and molecular biology. One of them is the “lipid divide”, that is, the difference of stereo structure of glycerophosphate of membrane lipid backbone and hydrocarbon chains. In this chapter, first, a quite unique structure and biosynthesis of archaeal membrane lipids are introduced and then a hypothesis on the differentiation of Archaea and Bacteria mainly driven by segregation of glycerophosphate enantiomers of lipid backbones and hydrocarbon chains in the universal common ancestor.