Bacterial cell division begins with polymerization of FtsZ protein and formation of Z‑ring, which marks the future site of the septum at the mid-cell. Z-ring serves as a scaffold for division proteins, and its proper placement is crucial for subsequent steps in cell division. In rod-shaped bacteria, one of the mechanisms responsible for correct placement of the division septum is the Min system. The action of Min system creates a concentration gradient of division inhibitor MinC, which is highest at the cell poles and lowest at the midcell. The underlying mechanism fundamentally differs between Escherichia coli and Bacillus subtilis though, the core components of the Min system, MinC and MinD, are evolutionary conserved. MinC, the direct inhibitor of FtsZ polymerization, is attracted to the membrane via MinD, whose localisation is in turn dependent on another protein/s called topological determinant. While in E. coli MinD protein undergoes rapid pole-to-pole oscillation driven by MinE protein, in B. subtilis MinD is anchored to the cell poles via MinJ/DivIVA complex.
In our previous study, we have shown that oscillating Min system of E. coli can be transplanted into B. subtilis. Interestingly, strains in which oscillation was observed were impaired in sporulation at the step of asymmetric septum formation [1]. The finding that oscillating Min system is not compatible with sporulation might partially explain why two Min systems with such distinct mechanism evolved for two different life cycles, vegetative growth and sporulation. Genome-wide search for Min system homologues in selected Gram-positive endospore-forming bacteria revealed that they harbour various combinations of homologues from both Min systems.
Two of the species carrying a combination of Min proteins from both systems Clostridium difficile (MinCDE, DivIVA) and Clostridium beijerinckii (MinCDE, MinJ/DivIVA) have been chosen for our further studies. Here we show the oscillatory behaviour of MinDE proteins of the two clostridial species in B. subtilis cells and investigate protein-protein interactions between Min proteins of these organisms [2]. We evaluated the effects of expression of these proteins on sporulation of B. subtilis.
This work was supported by Grant 2/0009/13 from the Slovak Academy of Sciences and by a Grant from the Slovak Research and Development Agency under contract APVV-14-018.