In another step toward creating artificial life, researchers have made spherical compartments with synthetic membranes that grow and divide in a coupled process (J. Am. Chem. Soc., DOI: 10.1021/ja900919c). Lab-made cells require a self-replicating lipid membrane, but current synthetic membranes must be forced through small pores to divide. What's more, the artificial cells tend to leak a sizable portion of their precious contents while dividing. Ting F. Zhu and Jack W. Szostak of Massachusetts General Hospital have improved upon those systems by encapsulating RNA inside a membrane consisting of multiple bilayers, instead of the single bilayer used in previous synthetic cell membranes. The new membranes grow in a surprising way, Szostak says. Rather than growing into larger spheres, they morph into long, threadlike structures. Gentle agitation of the threads couples their growth to a division process that leads to daughter spheres—with only a trace of RNA leakage. The model membranes undergo multiple cycles of growth and division, and the process works with a range of lipid components. The team's next goal is to encapsulate self-replicating nucleic acids inside this type of membrane, Szostak says.
Adding more fatty acid to Zhu and Szostak's lipid membrane container triggers a dramatic transformation, as captured by an epifluorescence microscope. The container changes from a sphere to a threadlike compartment. Gentle agitation from puffs of air helps the "thread" break into daughter spheres.