ARCHAELLUM · Assembly and function of the crenarchaeal flagellum

Archaea constitute the third domain of life and are believed to be close to the origin of life. They comprise a diverse group of micro-organisms that combine bacterial and eukaryotic features, but also employ many novel mechanisms. They possess a unique cell envelope with a cytoplasmic membrane of ether lipids surrounded by a proteinaceous S-layer and various cell appendages such as flagella, pili and more unusual structures. Studies have shown that the archaeal flagellum is an unique structure as it functionally resembles the bacterial flagellum, but structurally it is a simple type IV pilus. Moreover, we have shown that this type IV pilus can rotate. Therefore I propose to name the archaeal flagellum, the archaellum, as it is fundamentally different from the bacterial flagellum.In this proposal I aim to understand the assembly and mechanism of rotation of the archaellum of the thermocacidophilic crenarchaen Sulfolobus acidocaldarius by using biochemical, genetic and biophysical methods. The main milestons are:- Biochemical and structural characterization of all archaellum subunits- To understand the assembly pathway of the archaellum and the interactions of its differentsubunits- To understand how rotation of the filament is achieved and which subunits are importantfor this movementThis work will identify a new, relatively simple motor complex that has evolved from primordial type IV pili assembly machineries and therefore uncover general principles of macromolecular assemblies at cellular surfaces and a novel mechanism to generate mechanical force that can be translated into movement.""