Peter Graumann

Research area

We are studying dynamic processes in bacteria. We are interested in several questions that involve the spatial organization and biochemistry of the cell: how is the shape of a bacterium established? How is the cell cycle regulated and driven, and how is DNA transferred between bacteria? As a model for Gram positive bacteria, we use Bacillus subtilis cells, which offer a superb genetic and cell biological system. A further focus of the laboratory centers around chromosome dynamics. We want to understand how chromosomes are organized (they possess a defined spatial arrangement) and segregated during the cell cycle, how segregation is coordinated with cell division and how replication initiation is regulated and coordinated with segregation and cytokinesis. Further projects deal with the visualization of repair events on the chromosome and with uptake of DNA from the environment at a single cell pole and incorporation of DNA in the host chromosome (competence). Key proteins investigated are DnaA, SMC (structural maintenance of chromosomes)-like proteins and cytoskeletal element MreB, as well as DNA translocases and recombinases. MreB forms dynamic filaments underneath the cell membrane, which are critical for the maintenance of cell shape as well as for the arrangement of cytosolic proteins. The ultimate goal of our work is to understand how the bacterial cell is organized in 3D, and how proteins and DNA are dynamically positioned within a non-compartmentalized cell.

 

Research project within Synmikro

Within the area of SYNMIKRO, we investigate the question how actin-like MreB filaments organize cell wall synthesis as well as intracellular processes. We have visualized filament dynamics with 100 nm resolution in live cells and study the interaction network of these dynamic structures. MreB as well as coiled coil rich (Ccrp) proteins play an important role in the pathogenesis of Helicobacter pylori cells. We study the role of cytoskeletal elements for infectivity in human pathogens. We further pursue the plan to utilize bacterial cytoskeletal elements to generate novel interaction surfaces and 3D interaction networks. MreB and coiled coil rich filament-proteins form various stable or dynamic self-organizing assemblies, either membrane-associated or cytosolic. Such filamentous structures will be employed as recombinatory assembly platform for enzymes and signaling cascades.

Together with several SYNMIKRO member groups, we study the bacterial cell cycle, specifically the mechanism of segregation of duplicated sister chromosomes. We can visualize single fluorescent molecules and study their dynamics in real time, which reveals insight into molecular mechanisms in time and space with high precision.