Cells grow their boundaries by incorporating newly synthesized lipids into their membranes as well as through fusion of intracellular vesicles. As these processes yield trans-bilayer imbalances in lipid numbers, cells must redistribute lipids across the bilayer to enable sustained growth. Using giant and large unilamellar vesicles (GUVs and LUVs, respectively), we here recapitulate cellular growth and division under various conditions of transmembrane 'flip flop' of lipids. By dynamically monitoring the changes in reduced volume, spontaneous curvature, and area difference of GUVs that grow by fusion of many small LUVs, the morphology of these growing 'synthetic cells' is quantified. We demonstrate, for membranes containing various flip flop-capable molecules, that curvature stresses are relieved, generating more symmetrically sized buds, without significantly compromising the membrane integrity. Further increasing the neck curvature is shown to lead to bud scission. The mechanisms presented here offer insights into cell growth and division, which are important for understanding early protocells and designing synthetic cells that are able to grow and divide. ... Read more

Cell division is a fundamental process essential for life, underpinning reproduction, development and tissue maintenance across all organisms and enabling population growth and evolutionary adaptation. Recreating this capability is, therefore, a central challenge in bottom–up synthetic biology, wherein the aim is to construct functional synthetic cells. In recent years, substantial progress has been made toward building a synthetic divisome through partial reconstitution of the protein machinery underlying cell division in vitro. Here, we review current strategies to mimic the key stages of division: symmetry breaking to define the division site, membrane deformation to drive constriction and, thus, shape changes of the cell, and the final abscission event. We critically assess the successes and limitations of these approaches and discuss how integrating multiple modules may enable the realization of a minimal, functional division system for synthetic cells. ... Read more