Spontaneous division of model protocell membranes*

Prior to the existence of phospholipid membranes, the ancestors of modern day cells likely had membranes consisting of much simpler molecules. On early Earth, these membranes would have provided the function that modern cell rely on proteins for - nutrient transport, growth and division - prompting the question of whether such functions can arise from a lipid-only system.

We show that fatty acids can self-assemble into giant unilamellar vesicles (GUVs) without the need for scaffolding droplets, substrates, or microfluidics. Remarkably, such GUVs are capable of spontaneously dividing upon an increase in surface area to volume ratio, instead of simply forming tubular vesicles. When nucleic acids are encapsulated, the protocells - membranous compartments containing nucleic acids - are able to divide into daughter protocells without apparent loss of content.

We find that the bilayer properties of fatty acid membranes depend on the pH and ionic strength of the surrounding solution, and explore how the differences between fatty acid membranes and the better-studied phospholipid systems enable the unusual self-assembly and morphology changes we see.