Molecular mechanisms of phospho-dependent regulation and assembly of the bacterial divisome – PhoCellDiv

Bacterial cell division is a temporally and spatially regulated process coordinated by a multi-protein complex called the divisome. The assembly of the divisome is initiated and organized by a highly conserved bacterial protein, the bacterial tubulin homologue FtsZ, which polymerizes to form a dynamic ring structure that marks the site of cell division. Following ring assembly, structural and accessory proteins are recruited in an ordered manner to build the functional cell division machinery. The precise molecular mechanisms of how the assembly and regulation of the cell division machinery is achieved remains elusive, even in extensively studied model organisms such as Escherichia coli or Bacillus subtilis. Despite more than two decades of research, only partial answers are available for important questions regarding the mechanisms of FtsZ function, such as the architecture of the Z-ring in vivo, the actual origin of the constrictive force, or yet the relationship between Z-ring assembly and remodeling of the bacterial cell wall. Furthermore, while genetic and biochemical studies of bacterial model systems have identified many interactions amongst cell division proteins, the overall topology, architecture and dynamics of the divisome as a (large) multi-protein complex are still largely unknown. The recent expansion of our knowledge in and beyond well-studied model organisms illustrates the enormous diversity of cell division mechanisms in bacterial species and the picture that emerges points towards species-specific mechanisms that have evolved in order to achieve and maintain their respective cell shape and to pass it to their progeny.

During the last decade, substantial evidence has been accumulated showing that reversible protein phosphorylation by eukaryotic-like serine/threonine protein kinases plays essential signaling roles in bacterial physiology. In this project, our central working hypothesis is that phosphorylation plays a crucial role in the spatio-temporal regulation and quaternary organization of the cell division machinery. The major objective of our proposal is to investigate phospho-dependent protein-protein interactions governing divisome assembly and regulation in Streptococcaceae and the Corynebacteriales, two bacterial suborders that include major human pathogens such as Streptococcus pneumoniae, Mycobacterium tuberculosis and Corynebacterium diphtheria. Our project is based on an integrative biology approach combining the fields of structural biology, bacterial signaling, phosphoproteomics, bacterial genetics and cell biology. The proposed collaborative effort and the complementary expertise of the partnership will allow us to dynamically communicate between molecular and cellular approaches, positioning this proposal in a competitive and timely framework at an international level. The scientific outcomes of this project will shed light on the regulation of a fundamental and cardinal process of bacterial cell biology. The benefits are diverse and range from an immediate knowledge of cell division of two model bacteria to the opening of new concepts concerning the inner-workings of a living cell right through the better understanding of the constantly growing role of phosphorylation in bacterial physiology. The concepts generated could thus set an example towards our understanding of the cell cycle of other bacteria. Furthermore, since cell division is fundamental to all forms of life, a better understanding of how bacteria divide at the molecular level is not only important for cell biology, but it is also expected to have a strong impact on biomedical research.