Question 7: construction of a semi-synthetic minimal cell: a model for early living cells.

Using a Synthetic Biology approach we are building a semi-synthetic minimal cell. This represents an exercise to shape a minimal-cell model system recalling the simplicity of early living cells in early evolution. We have recently introduced into liposome compartments a minimal set of enzymes named "Puresystem" (PS) synthesizing EGFP proteins. To establish reproduction of the shell compartment with a minimal set of genes we have cloned the genes for the Fatty Acid Synthase (FAS) type I enzymes. These FAS genes introduced into liposomes, translated into FAS enzymes by PS and in the presence of precursors produce fatty acids. The resulting release of fatty acid molecules within liposome vesicles should promote vesicle growth and reproduction. The core reproduction of a minimal cell corresponding to the replication of the minimal genome will require a few genes for the DNA replication and the PS, and a minimum set of genes for the synthesis of t-RNAs. In future the reconstruction of a minimal ribosome will bring the number of genes for ribosomal proteins from 54 of an existing minimal genome down to 30-20 genes. A Synthetic Biology approach could bring the number of essential genes for a minimal cell down to 100 or less.