Actin-like cytoskeletal systems in bacteria and archaea

Many bacteria and archaea contain cytomotive filaments consisting of proteins that are related in subunit and protofilament structure to eukaryotic actin. Our goal is to understand the molecular mechanisms that these filaments and their accessory factors employ in order to facilitate a diverse set of cell biological phenomena. We propose to discover how MreB maintains cell shape in non-round cells and, in particular, what is the role of filaments in this system. We will investigate MamK and how it aligns magnetosomes along its filaments. ParM filaments form antiparallel spindles during plasmid segregation and we propose to unravel the ParRC-accelerated formin-like polymerisation mechanism at the filament tips. Also, we plan to work on not so well-characterised systems such as crenactin and other Alps for which basic functions need to be discovered. Finally, we will work on technology developments for electron cryotomography, producing clonable, monovalent ferritin-based electron dense labels and performing FIB milling procedures that yield isotropic maps of entire cells containing filaments at molecular resolution. Overall, we will discover and describe how cytomotive filament systems with actin at their centre, presumably having originated from a simple common ancestor, developed into sophisticated machinery that operates on otherwise inaccessible length scales.