A tuneable minimal cell membrane reveals that two lipid species suffice for life

All cells are encapsulated by a lipid membrane that facilitates their interactions with the environment. How cells manage diverse mixtures of lipids, which dictate membrane property and function, is experimentally challenging to address. Here, we present an approach to tune and minimize membrane lipid composition in the bacterium Mycoplasma mycoides and its derived ‘minimal cell’ (JCVI-Syn3A), revealing that a two-component lipidome can support life. Systematic reintroduction of phospholipids with different features demonstrates that acyl chain diversity is more important for growth than head group diversity. By tuning lipid chirality, we explore the lipid divide between Archaea and the rest of life, showing that ancestral lipidomes could have been heterochiral. However, in these simple organisms, heterochirality leads to impaired cellular fitness. Thus, our approach offers a tunable minimal membrane system to explore the fundamental lipidomic requirements for life, thereby extending the concept of minimal life from the genome to the lipidome. All cells are encapsulated by a membrane of complex lipidic composition, and understanding the roles of different lipids in membrane function is experimentally challenging to address. Here, Justice et al. present an approach to minimize and tune the membrane lipid composition in a ‘minimal’ bacterial cell, revealing that two lipid species can support life.