Fluorescence Studies of Cell Division in Escherichia coli

Sammanfattning: In Escherichia coli the cell division is carried out by a large dynamic protein complex called the divisome. The divisome assembles in a two-step manner starting with the localization of the eukaryotic tubulin homologue FtsZ to the midcell. Together with other early arriving proteins FtsZ form an intermediate structure called the Z-ring. After a considerable time lag the divisome maturates fully by recruiting several other late arriving proteins before it starts to constrict the cell envelope that ultimately will lead to cytokinesis and the formation of two identical daughter cells. Despite of being objectives of extensive study over the last decades, understanding of the exact molecular roles of many of the divisome proteins is still lacking and to date there is very limited knowledge of the disassembly process of the divisome. In this thesis I have used various fluorescence microscopy based methods to better characterize the role of FtsZ and other divisome proteins during the final stages of the cell division. I have shown that FtsZ disassembles from the divisome prior to inner membrane closure indicating that it is not the force generator during this final step of division that it is widely thought to be. I have also shown that the disassembly of the divisome is a multistep process in which the proteins that arrive in the second step of divisome assembly also remain at the division septum longer than those proteins that arrive in the first step. These findings add new important information regarding the cell division and together they provide a more complete picture of this event that ultimately may lead to more efficient identification of novel antibiotic targets.