How do bacteria localize macromolecular complexes at their cell pole?

Bacteria are unicellular organisms, as well as infectious agents, causative of multiple diseases. Since the 1950's, the threat of bacterial infections had largely subsided, due to the development of antibiotics. However, bacteria have showed an increasing amount of resistance to these in recent years. Indeed, we are fast-approaching a post-antibiotic world: an estimated 1.2 M people die annually from antibiotic-resistant bacterial infections world-wide, and projections indicate that this number will increase to ~ 10 M/year by 2050. We therefore urgently need to identify new approaches to combat bacterial infections.
A previously-underappreciated aspect of bacteria is that they possess a very tightly-regulated internal organization, to ensure the proper localization of its various components and organelles, notably during cell division. In particular, a family of proteins (permed ParA/FlhG/MinD) is ubiquitous in bacteria, and has been shown to regulate the positioning of molecules and organelles at the pole of the cell. However, the mechanism of action of this family is currently not understood at the molecular level.
Here, we propose to use a range of biophysical techniques to determine the general mechanism of action of this family of proteins. Specifically, we propose that the propensity of these proteins to form filaments, driving their cargo across the cell, is central to their function. We will notably exploit recent advances in cryo-electron microscopy, and in Artificial Intelligence-driven modelling, to understand how these proteins assemble at the atomic level, and how it allows them to recruit their respective cargo at the cell pole.
This proposal will provide a fundamental shift in our understanding of bacterial cell biology, and could lead to the development of novel antibacterial therapeutics.

For decades, bacteria have been considered 'bags of enzymes', merely vesicles containing proteins and nucleic acids but lacking any internal order. However it has become apparent in the past ~30 years that their internal organization is actually very intricately regulated, with a complex cytoskeleton responsible for trafficking DNA and proteins across the cell. Notably, one key aspect in this organization is the positioning of a range of macromolecular complexes at the cell pole. This is critical to ensure the proper functioning of the cell, including features such as motility and chemotaxis, and to allow efficient cell division.

A single family of proteins, the ParA/FlhG/MinD family, is intimately linked with these various processes, and homologues are notably involved in DNA segregation, flagellum and pili localization, chemoreceptor and microcompartment positioning, and more. Nonetheless, the basic principles that dictates the mechanism of action of this protein family in pole localization remain very poorly understood. Building on our previous work on both plasmid segregation and bacterial flagellum assembly, we hypothesize that a central aspect of this family of proteins' function is their propensity to form higher-order oligomers, using either DNA or the cell membranes as a template.

To verify this, we will employ a range of biochemical, biophysical and structural methods, to decipher the molecular details of their filamentous structure, how it affects their recruitment of their respective cargo, and their localization to the cell pole. This innovative, integrative approach will allow us to move beyond the classical, descriptive characterization of each process in isolation and for single bacteria, towards a global vision of how macromolecules are localized within the bacterial cell.