The morphology of rod shaped bacteria is achieved through two very dynamic synthetic complexes: the elongasome and the divisome. The elongasomes are recruited by the actin-like cytoskeleton MreB protein underneath the plasma membrane and move in an helical path to insert new peptidoglycan subunits to elongate the cell envelope whereas the divisome is responsible for division and the synthesis of new cell poles. Cell division is directed by the FtsZ ring (a tubulin homolog) that directs the synthesis of the new cell poles during binary fission by treadmilling in a ring underneath the cytoplasmic membrane. The assembly and the dynamics of the elongasome and divisome are studied in vivo using immunofluorescence and fluorescence microscopy techniques (FRET, FLIM, FRAP, immunolocalization) and in vitro using state of the art biochemical and biophysical techniques. By aiming to obtain quantitative data on number of proteins, their affinities for each other or their substrates and their localization as function of the bacterial division cycle, we hope to model the measured and observed interactions. Similar studies are directed to the insertion of outer membrane proteins and the lipid and LPS transport systems that enable envelope membrane growth. The crosstalk between these protein machines could provide new targets for antibiotics that attack multiple essential pathways in the cell and so make it much harder for the bacteria to become resistant to these antibiotics.
Figure 1. A. Schematic presentation of the timing of cell division cycle event. B. Many proteins are involved in cell division and are collectively termed the divisome. About 50 synthetic complexes (green spheres) are recruited by the FtsZ ring (orange ring). While the ring constrict the synthetic complexes synthesize the new cell poles and split the envelope between the two daughter cells simultaneously. C. MreB polymers underneath the cytoplasmic membrane recruit the synthetic complexes (elongasomes) involved in length growth.