Membrane remodelling during cell division in the thermoacidiophilic archaeaon Sulfolobus acidocaldarius

At division, the cellular membrane undergoes rapid and large-scale changes in shape and lipid composition. While these changes have been characterised in a number of eukaryotes and bacteria, almost nothing is known about the role of the membrane in archaeal cell division. Archaeal lipids are chemically distinct and membranes play an especially critical, structural role for archaeal cells that lack a cell wall. This is the case for Sulfolobus acidocaldarius, a model thermoacidophilic archaeon that is currently the closest experimentally tractable relative of eukaryotes. While cell division in Sulfolobus is driven by the activity of ESCRTIII and Vps4 - homologues of the proteins catalysing abscission in many eukaryotes - the lipid membrane that ESCRTIII remodels in Sulfolobus has a unique chemistry and organisation. Distinct from bacterial or eukaryotic lipids, archaeal lipids can span the membrane to create an effective monolayer. Using a combination of high temperature live-cell imaging, lipidomics and structural studies, I aim to determine the properties of the archaeal lipid membrane that are necessary to support ESCRTIII function in archaeal cell division. To do so I will: 1) create new tools for visualising membrane dynamics in archaea using both commercially available and newly synthesised lipid probes in live cell microscopy; 2) identify the spatial and temporal control of lipids and membrane properties during cell division using a combination of lipidomics, proteomics and microscopy; 3) characterise how ESCRTIII interacts with the archaeal membrane using structural techniques and in silico modelling. Through understanding of how conserved proteins can act on such different membrane architectures we hope to shed some light on fundamental principles of cell division as well as the evolution of the comparatively more complex division machinery of eukaryotes.