Coordination mechanisms between cell division and chromosome segregation in E. coli

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PROJECT SUMMARY/ABSTRACT The aim of the proposed work is to investigate key coordination mechanisms between cell division and chromosome segregation to enhance our understanding of fundamental cellular processes in bacteria. Proper spatial and temporal coordination between cell division and chromosome segregation must guarantee that chromosomes partition correctly to daughter cells. In Escherichia coli and many other bacterial species the first step in reliable partitioning of chromosomes is achieved via proper positioning of cell division proteins: the divisome. Three molecular systems in E. coli are known to regulate the assembly of FtsZ filaments to an early divisome (the Z-ring). These include the Min system and the nucleoid occlusion factor SlmA, which both determine the localization of the Z-ring via negative regulation. We recently discovered that E. coli also harbors a positive regulatory system, referred to as the Ter linkage. Z-ring associated proteins ZapA, ZapB and DNA binding protein MatP are involved in this mechanism. In addition to positioning of the Z-ring, the movement of chromosomes in late stages of cell division is also responsible for their proper partitioning. In E. coli DNA pump FtsK is the main source of this movement but it might not be the only one. Although the key factors comprising these coordination systems have been identified and many protein-protein interactions mapped out, there is limited understanding of how these interactions collectively lead to dynamic cellular level behaviors. In particular, there is only a very approximate understanding how and when Z-ring forms. There is also limited knowledge how chromosomal DNA moves and is partitioned during cell division. Both processes are essential for cell survival. This proposal will fill these gaps by combining molecular biology and genetic tools with novel state-of-the art microscopy and image analysis techniques. In addition to experimental studies we will use computer modelling to develop a conceptual framework for these processes. Specifically, we will determine how FtsZ protofilaments form and assemble to a cohesive Z-ring in the cell (Aim 1). We will also investigate how these steps are influenced spatially and temporally by coupling between Z-ring and replication terminus region of the chromosome via the Ter linkage proteins (Aim 2). In addition to studying how bacterial nucleoids affect cell division we will also determine how cell division acts on nucleoids and moves chromosomal DNA during cell division (Aim 3). The knowledge gained from this project will enhance our understanding of fundamental cellular processes in bacteria and provide a framework for designing effective antibacterial therapies to combat multidrug resistant bacteria.