Membranes of all living cells are composed of (phospho-) lipids assembled into a lipid bilayer, which separates the cells inside from the outside. Depending on the environmental conditions, membranes need different properties to form a suitable barrier. For example, the membranes of archaeal extremophiles need to withstand harsh environmental conditions (high temperatures, salt concentrations, pH, etc.). Therefore, their membranes consist of completely different types of lipids, than for instance the membrane of the model bacterium Escherichia coli.
In this group we study the different types of lipids that are out there. We try to figure out the way they are synthesized and understand their specific function. In this way, we hope to contribute to the general understanding of the lipid membrane synthesis, composition, and regulation. Ultimately, we would like to mimic these processes in the context of a synthetic cell.
‘Cardiolipin’ usually refers to: 1,3-bis(sn-3’-phosphatidyl)-sn-glycerol (Gro-DPCL), but this lipid species is one of the many various cardiolipins that have been identified. Currently, there are some indications that their production might play a role in the membrane response to certain environmental conditions, but the role of cardiolipins in this process remains to be discovered. A crucial aspect in this will be the unraveling of their enzymatic synthesis. Once the enzymes involved are identified, cardiolipin production can be controlled and the effects studied. Recently, we discovered that an archaeal cardiolipin synthase was capable of synthesizing a wide variety of different cardiolipin species, but not all different sub-classes.
Currently, we are trying to identify similar enzymes with the aim to further discover the enzymatic synthesis of cardiolipins. After the enzymatic synthesis routes have been identified, we can systematically target the enzymes involved and study the role of cardiolipins in vivo.
One of the major challenges in synthetic biology is the bottom-up construction of a synthetic cell. A key feature of such a cell will be its ability to grow and divide, which includes growth of the cellular membrane. Previously, an in vitro phospholipid biosynthesis pathway has been developed that converts simple building blocks into mature phospholipids. The production levels were large enough to observe membrane growth, but further optimization is needed to develop this pathway into a sustainable membrane expansion module.
The developed synthetic pathway forms an excellent starting point to study the phospholipid biosynthesis machinery as a complete entity both in vitro and in vivo. A couple of questions we would like to address are: Do the individual components of the machinery interact with each other? Is there a coupling between membrane growth and cell division? Eventually, this research should help us further progress towards a replicating synthetic cell.